Create SaaS invoicing application with FastAPI and SQLite

- Set up project structure with modular organization - Implement database models for users, organizations, clients, invoices - Create Alembic migration scripts for database setup - Implement JWT-based authentication and authorization - Create API endpoints for users, organizations, clients, invoices - Add PDF generation for invoices using ReportLab - Add comprehensive documentation in README
2025-06-06 11:21:11 +00:00 · 2025-06-06 11:21:11 +00:00 · c8aed27755
commit c8aed27755
parent 388534ec6c
43 changed files with 2214 additions and 2 deletions
--- a/README.md
+++ b/README.md
@ -1,3 +1,203 @@
-# FastAPI Application
+# SaaS Invoicing Application

-This is a FastAPI application bootstrapped by BackendIM, the AI-powered backend generation platform.
+A comprehensive SaaS invoicing application built with FastAPI and SQLite, designed for businesses to manage organizations, clients, and invoices efficiently.
+
+## Features
+
+- **Multi-tenant Architecture**: Supports multiple organizations with user management
+- **User Authentication**: Secure JWT-based authentication and role-based permissions
+- **Organization Management**: Create and manage organizations with detailed information
+- **Client Management**: Maintain a database of clients for each organization
+- **Invoice Management**: Create, update, and delete invoices with line items
+- **PDF Generation**: Generate professional PDF invoices for sharing with clients
+- **API Documentation**: Interactive API documentation with Swagger UI and ReDoc
+
+## Prerequisites
+
+- Python 3.8+
+- pip (Python package manager)
+
+## Environment Variables
+
+The application uses the following environment variables:
+
+| Variable | Description | Default Value |
+|----------|-------------|---------------|
+| SECRET_KEY | Secret key for JWT token generation | CHANGE_ME_TO_A_SECURE_RANDOM_STRING |
+| ACCESS_TOKEN_EXPIRE_MINUTES | Access token expiration time in minutes | 30 |
+| SERVER_HOST | Host URL for the server | http://localhost:8000 |
+
+## Installation
+
+1. Clone the repository:
+
+```bash
+git clone https://github.com/yourusername/saasinvoicingapplication.git
+cd saasinvoicingapplication
+```
+
+2. Create a virtual environment (optional but recommended):
+
+```bash
+python -m venv venv
+source venv/bin/activate  # On Windows: venv\Scripts\activate
+```
+
+3. Install dependencies:
+
+```bash
+pip install -r requirements.txt
+```
+
+4. Create a `.env` file with your environment variables:
+
+```
+SECRET_KEY=your-secure-secret-key
+ACCESS_TOKEN_EXPIRE_MINUTES=30
+SERVER_HOST=http://localhost:8000
+```
+
+5. Initialize the database:
+
+```bash
+mkdir -p /app/storage/db
+python -c "from app.db.base import Base; from app.db.session import engine; Base.metadata.create_all(bind=engine)"
+alembic upgrade head
+```
+
+## Running the Application
+
+Start the application using uvicorn:
+
+```bash
+uvicorn main:app --host 0.0.0.0 --port 8000 --reload
+```
+
+The API will be available at:
+- API: http://localhost:8000
+- Swagger UI Documentation: http://localhost:8000/docs
+- ReDoc Documentation: http://localhost:8000/redoc
+
+## API Structure
+
+The API follows a RESTful design and is structured as follows:
+
+### Authentication Endpoints
+
+- `POST /api/v1/auth/token` - Get access token
+- `POST /api/v1/auth/test-token` - Test token validity
+
+### User Management
+
+- `GET /api/v1/users/` - List users (admin only)
+- `POST /api/v1/users/` - Create user (admin only)
+- `GET /api/v1/users/me` - Get current user info
+- `PUT /api/v1/users/me` - Update current user
+- `GET /api/v1/users/{user_id}` - Get user by ID
+- `PUT /api/v1/users/{user_id}` - Update user (admin only)
+
+### Organization Management
+
+- `GET /api/v1/organizations/` - List organizations
+- `POST /api/v1/organizations/` - Create organization (admin only)
+- `GET /api/v1/organizations/{id}` - Get organization by ID
+- `PUT /api/v1/organizations/{id}` - Update organization
+- `DELETE /api/v1/organizations/{id}` - Delete organization (admin only)
+
+### Client Management
+
+- `GET /api/v1/clients/` - List clients
+- `POST /api/v1/clients/` - Create client
+- `GET /api/v1/clients/{id}` - Get client by ID
+- `PUT /api/v1/clients/{id}` - Update client
+- `DELETE /api/v1/clients/{id}` - Delete client
+
+### Invoice Management
+
+- `GET /api/v1/invoices/` - List invoices
+- `POST /api/v1/invoices/` - Create invoice
+- `GET /api/v1/invoices/{id}` - Get invoice by ID
+- `PUT /api/v1/invoices/{id}` - Update invoice
+- `DELETE /api/v1/invoices/{id}` - Delete invoice
+- `GET /api/v1/invoices/{id}/pdf` - Generate PDF for invoice
+
+## Data Models
+
+### User
+
+- `id`: Unique identifier
+- `email`: Email address (unique)
+- `full_name`: Full name
+- `hashed_password`: Hashed password
+- `is_active`: User status
+- `is_superuser`: Admin status
+- `organization_id`: Associated organization
+
+### Organization
+
+- `id`: Unique identifier
+- `name`: Organization name
+- `address`, `city`, `state`, `postal_code`, `country`: Address information
+- `phone`, `email`, `website`: Contact information
+- `tax_id`: Tax identification number
+- `logo_url`: URL to organization logo
+
+### Client
+
+- `id`: Unique identifier
+- `name`: Client name
+- `contact_name`: Primary contact
+- `email`, `phone`: Contact information
+- `address`, `city`, `state`, `postal_code`, `country`: Address information
+- `tax_id`: Tax identification number
+- `notes`: Additional notes
+- `organization_id`: Associated organization
+- `created_by_id`: User who created the client
+
+### Invoice
+
+- `id`: Unique identifier
+- `invoice_number`: Invoice reference number
+- `status`: Invoice status (draft, sent, paid, overdue, cancelled)
+- `issue_date`, `due_date`: Invoice dates
+- `subtotal`, `tax_rate`, `tax_amount`, `discount`, `total`: Financial information
+- `notes`, `terms`: Additional information
+- `is_recurring`, `recurring_interval`: Recurring invoice details
+- `client_id`: Associated client
+- `organization_id`: Associated organization
+- `created_by_id`: User who created the invoice
+
+### InvoiceItem
+
+- `id`: Unique identifier
+- `description`: Item description
+- `quantity`, `unit_price`, `amount`: Item details
+- `invoice_id`: Associated invoice
+
+## Development
+
+### Running Tests
+
+Run tests using pytest:
+
+```bash
+pytest
+```
+
+### Database Migrations
+
+Generate a new migration after model changes:
+
+```bash
+alembic revision --autogenerate -m "Description of changes"
+```
+
+Apply migrations:
+
+```bash
+alembic upgrade head
+```
+
+## License
+
+This project is licensed under the MIT License - see the LICENSE file for details.
--- a/alembic.ini
+++ b/alembic.ini
@ -0,0 +1,84 @@
+# A generic, single database configuration.
+
+[alembic]
+# path to migration scripts
+script_location = migrations
+
+# template used to generate migration files
+# file_template = %%(rev)s_%%(slug)s
+
+# timezone to use when rendering the date
+# within the migration file as well as the filename.
+# string value is passed to dateutil.tz.gettz()
+# leave blank for localtime
+# timezone =
+
+# max length of characters to apply to the
+# "slug" field
+# truncate_slug_length = 40
+
+# set to 'true' to run the environment during
+# the 'revision' command, regardless of autogenerate
+# revision_environment = false
+
+# set to 'true' to allow .pyc and .pyo files without
+# a source .py file to be detected as revisions in the
+# versions/ directory
+# sourceless = false
+
+# version location specification; this defaults
+# to migrations/versions.  When using multiple version
+# directories, initial revisions must be specified with --version-path
+# version_locations = %(here)s/bar %(here)s/bat migrations/versions
+
+# the output encoding used when revision files
+# are written from script.py.mako
+# output_encoding = utf-8
+
+sqlalchemy.url = sqlite:////app/storage/db/db.sqlite
+
+[post_write_hooks]
+# post_write_hooks defines scripts or Python functions that are run
+# on newly generated revision scripts.  See the documentation for further
+# detail and examples
+
+# format using "black" - use the console_scripts runner, against the "black" entrypoint
+# hooks=black
+# black.type=console_scripts
+# black.entrypoint=black
+# black.options=-l 79
+
+# Logging configuration
+[loggers]
+keys = root,sqlalchemy,alembic
+
+[handlers]
+keys = console
+
+[formatters]
+keys = generic
+
+[logger_root]
+level = WARN
+handlers = console
+qualname =
+
+[logger_sqlalchemy]
+level = WARN
+handlers =
+qualname = sqlalchemy.engine
+
+[logger_alembic]
+level = INFO
+handlers =
+qualname = alembic
+
+[handler_console]
+class = StreamHandler
+args = (sys.stderr,)
+level = NOTSET
+formatter = generic
+
+[formatter_generic]
+format = %(levelname)-5.5s [%(name)s] %(message)s
+datefmt = %H:%M:%S
--- a/app/api/init.py
+++ b/app/api/init.py
@ -0,0 +1 @@
+# API package initialization
--- a/app/api/deps.py
+++ b/app/api/deps.py
@ -0,0 +1,54 @@
+
+from fastapi import Depends, HTTPException, status
+from fastapi.security import OAuth2PasswordBearer
+from jose import jwt
+from pydantic import ValidationError
+from sqlalchemy.orm import Session
+
+from app import models, schemas
+from app.core.config import settings
+from app.db.session import get_db
+
+oauth2_scheme = OAuth2PasswordBearer(
+    tokenUrl=f"{settings.API_V1_STR}/auth/token"
+)
+
+
+def get_current_user(
+    db: Session = Depends(get_db),
+    token: str = Depends(oauth2_scheme)
+) -> models.User:
+    try:
+        payload = jwt.decode(
+            token,
+            settings.SECRET_KEY,
+            algorithms=[settings.ALGORITHM]
+        )
+        token_data = schemas.TokenPayload(**payload)
+    except (jwt.JWTError, ValidationError):
+        raise HTTPException(
+            status_code=status.HTTP_403_FORBIDDEN,
+            detail="Could not validate credentials",
+        )
+    user = db.query(models.User).filter(models.User.id == token_data.sub).first()
+    if not user:
+        raise HTTPException(status_code=404, detail="User not found")
+    return user
+
+
+def get_current_active_user(
+    current_user: models.User = Depends(get_current_user),
+) -> models.User:
+    if not current_user.is_active:
+        raise HTTPException(status_code=400, detail="Inactive user")
+    return current_user
+
+
+def get_current_active_superuser(
+    current_user: models.User = Depends(get_current_user),
+) -> models.User:
+    if not current_user.is_superuser:
+        raise HTTPException(
+            status_code=400, detail="The user doesn't have enough privileges"
+        )
+    return current_user
--- a/app/api/v1/init.py
+++ b/app/api/v1/init.py
@ -0,0 +1 @@
+# API v1 package initialization
--- a/app/api/v1/api.py
+++ b/app/api/v1/api.py
@ -0,0 +1,10 @@
+from fastapi import APIRouter
+
+from app.api.v1.endpoints import auth, users, organizations, clients, invoices
+
+api_router = APIRouter()
+api_router.include_router(auth.router, prefix="/auth", tags=["authentication"])
+api_router.include_router(users.router, prefix="/users", tags=["users"])
+api_router.include_router(organizations.router, prefix="/organizations", tags=["organizations"])
+api_router.include_router(clients.router, prefix="/clients", tags=["clients"])
+api_router.include_router(invoices.router, prefix="/invoices", tags=["invoices"])
--- a/app/api/v1/endpoints/init.py
+++ b/app/api/v1/endpoints/init.py
@ -0,0 +1 @@
+# API endpoints package initialization
--- a/app/api/v1/endpoints/auth.py
+++ b/app/api/v1/endpoints/auth.py
@ -0,0 +1,50 @@
+from datetime import timedelta
+from typing import Any
+
+from fastapi import APIRouter, Depends, HTTPException, status
+from fastapi.security import OAuth2PasswordRequestForm
+from sqlalchemy.orm import Session
+
+from app import crud, models, schemas
+from app.api import deps
+from app.core import security
+from app.core.config import settings
+
+router = APIRouter()
+
+
+@router.post("/token", response_model=schemas.Token)
+def login_access_token(
+    db: Session = Depends(deps.get_db),
+    form_data: OAuth2PasswordRequestForm = Depends()
+) -> Any:
+    """
+    OAuth2 compatible token login, get an access token for future requests
+    """
+    user = crud.user.authenticate(
+        db, email=form_data.username, password=form_data.password
+    )
+    if not user:
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail="Incorrect email or password",
+        )
+    elif not user.is_active:
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST, detail="Inactive user"
+        )
+    access_token_expires = timedelta(minutes=settings.ACCESS_TOKEN_EXPIRE_MINUTES)
+    return {
+        "access_token": security.create_access_token(
+            user.id, expires_delta=access_token_expires
+        ),
+        "token_type": "bearer",
+    }
+
+
+@router.post("/test-token", response_model=schemas.User)
+def test_token(current_user: models.User = Depends(deps.get_current_user)) -> Any:
+    """
+    Test access token
+    """
+    return current_user
--- a/app/api/v1/endpoints/clients.py
+++ b/app/api/v1/endpoints/clients.py
@ -0,0 +1,137 @@
+from typing import Any, List
+
+from fastapi import APIRouter, Depends, HTTPException
+from sqlalchemy.orm import Session
+
+from app import crud, models, schemas
+from app.api import deps
+
+router = APIRouter()
+
+
+@router.get("/", response_model=List[schemas.Client])
+def read_clients(
+    db: Session = Depends(deps.get_db),
+    skip: int = 0,
+    limit: int = 100,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Retrieve clients.
+    """
+    if crud.user.is_superuser(current_user):
+        clients = crud.client.get_multi(db, skip=skip, limit=limit)
+    elif current_user.organization_id:
+        # Filter clients by the user's organization
+        clients = (
+            db.query(models.Client)
+            .filter(models.Client.organization_id == current_user.organization_id)
+            .offset(skip)
+            .limit(limit)
+            .all()
+        )
+    else:
+        clients = []
+    return clients
+
+
+@router.post("/", response_model=schemas.Client)
+def create_client(
+    *,
+    db: Session = Depends(deps.get_db),
+    client_in: schemas.ClientCreate,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Create new client.
+    """
+    # Ensure user has permission to create a client for the specified organization
+    if not crud.user.is_superuser(current_user) and (
+        current_user.organization_id != client_in.organization_id
+    ):
+        raise HTTPException(status_code=400, detail="Not enough permissions")
+    
+    # Create client with created_by information
+    client_data = client_in.dict()
+    client = models.Client(**client_data, created_by_id=current_user.id)
+    db.add(client)
+    db.commit()
+    db.refresh(client)
+    return client
+
+
+@router.get("/{id}", response_model=schemas.Client)
+def read_client(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Get client by ID.
+    """
+    client = crud.client.get(db, id=id)
+    if not client:
+        raise HTTPException(status_code=404, detail="Client not found")
+    if not crud.user.is_superuser(current_user) and (
+        current_user.organization_id != client.organization_id
+    ):
+        raise HTTPException(status_code=400, detail="Not enough permissions")
+    return client
+
+
+@router.put("/{id}", response_model=schemas.Client)
+def update_client(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    client_in: schemas.ClientUpdate,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Update a client.
+    """
+    client = crud.client.get(db, id=id)
+    if not client:
+        raise HTTPException(status_code=404, detail="Client not found")
+    
+    if not crud.user.is_superuser(current_user) and (
+        current_user.organization_id != client.organization_id
+    ):
+        raise HTTPException(status_code=400, detail="Not enough permissions")
+    
+    # Prevent changing organization_id if not a superuser
+    if (
+        client_in.organization_id is not None
+        and client_in.organization_id != client.organization_id
+        and not crud.user.is_superuser(current_user)
+    ):
+        raise HTTPException(
+            status_code=400, detail="Cannot change client's organization"
+        )
+    
+    client = crud.client.update(db, db_obj=client, obj_in=client_in)
+    return client
+
+
+@router.delete("/{id}", response_model=schemas.Client)
+def delete_client(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Delete a client.
+    """
+    client = crud.client.get(db, id=id)
+    if not client:
+        raise HTTPException(status_code=404, detail="Client not found")
+    
+    if not crud.user.is_superuser(current_user) and (
+        current_user.organization_id != client.organization_id
+    ):
+        raise HTTPException(status_code=400, detail="Not enough permissions")
+    
+    client = crud.client.remove(db, id=id)
+    return client
--- a/app/api/v1/endpoints/invoices.py
+++ b/app/api/v1/endpoints/invoices.py
@ -0,0 +1,201 @@
+from typing import Any, List
+from datetime import datetime
+
+from fastapi import APIRouter, Depends, HTTPException, Response
+from sqlalchemy.orm import Session
+
+from app import crud, models, schemas
+from app.api import deps
+from app.services.pdf_generator import generate_invoice_pdf
+
+router = APIRouter()
+
+
+@router.get("/", response_model=List[schemas.Invoice])
+def read_invoices(
+    db: Session = Depends(deps.get_db),
+    skip: int = 0,
+    limit: int = 100,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Retrieve invoices.
+    """
+    if crud.user.is_superuser(current_user):
+        invoices = crud.invoice.get_multi(db, skip=skip, limit=limit)
+    elif current_user.organization_id:
+        # Filter invoices by the user's organization
+        invoices = (
+            db.query(models.Invoice)
+            .filter(models.Invoice.organization_id == current_user.organization_id)
+            .offset(skip)
+            .limit(limit)
+            .all()
+        )
+    else:
+        invoices = []
+    return invoices
+
+
+@router.post("/", response_model=schemas.Invoice)
+def create_invoice(
+    *,
+    db: Session = Depends(deps.get_db),
+    invoice_in: schemas.InvoiceCreate,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Create new invoice.
+    """
+    # Verify organization access
+    if not crud.user.is_superuser(current_user) and (
+        current_user.organization_id != invoice_in.organization_id
+    ):
+        raise HTTPException(status_code=400, detail="Not enough permissions")
+    
+    # Verify client belongs to the organization
+    client = crud.client.get(db, id=invoice_in.client_id)
+    if not client or client.organization_id != invoice_in.organization_id:
+        raise HTTPException(status_code=400, detail="Invalid client for this organization")
+    
+    # Create invoice
+    invoice_data = invoice_in.dict(exclude={"items"})
+    invoice = models.Invoice(**invoice_data, created_by_id=current_user.id)
+    db.add(invoice)
+    db.commit()
+    db.refresh(invoice)
+    
+    # Create invoice items
+    for item_data in invoice_in.items:
+        item = models.InvoiceItem(**item_data.dict(), invoice_id=invoice.id)
+        db.add(item)
+    
+    db.commit()
+    db.refresh(invoice)
+    return invoice
+
+
+@router.get("/{id}", response_model=schemas.Invoice)
+def read_invoice(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Get invoice by ID.
+    """
+    invoice = crud.invoice.get(db, id=id)
+    if not invoice:
+        raise HTTPException(status_code=404, detail="Invoice not found")
+    
+    if not crud.user.is_superuser(current_user) and (
+        current_user.organization_id != invoice.organization_id
+    ):
+        raise HTTPException(status_code=400, detail="Not enough permissions")
+    
+    return invoice
+
+
+@router.put("/{id}", response_model=schemas.Invoice)
+def update_invoice(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    invoice_in: schemas.InvoiceUpdate,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Update an invoice.
+    """
+    invoice = crud.invoice.get(db, id=id)
+    if not invoice:
+        raise HTTPException(status_code=404, detail="Invoice not found")
+    
+    if not crud.user.is_superuser(current_user) and (
+        current_user.organization_id != invoice.organization_id
+    ):
+        raise HTTPException(status_code=400, detail="Not enough permissions")
+    
+    # Prevent changing organization_id if not a superuser
+    if (
+        invoice_in.organization_id is not None
+        and invoice_in.organization_id != invoice.organization_id
+        and not crud.user.is_superuser(current_user)
+    ):
+        raise HTTPException(
+            status_code=400, detail="Cannot change invoice's organization"
+        )
+    
+    # Update basic invoice data
+    update_data = invoice_in.dict(exclude={"items"}, exclude_unset=True)
+    for field, value in update_data.items():
+        setattr(invoice, field, value)
+    
+    # Update invoice items if provided
+    if invoice_in.items:
+        # Delete existing items
+        db.query(models.InvoiceItem).filter(models.InvoiceItem.invoice_id == id).delete()
+        
+        # Create new items
+        for item_data in invoice_in.items:
+            item = models.InvoiceItem(**item_data.dict(), invoice_id=id)
+            db.add(item)
+    
+    db.commit()
+    db.refresh(invoice)
+    return invoice
+
+
+@router.delete("/{id}", response_model=schemas.Invoice)
+def delete_invoice(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Delete an invoice.
+    """
+    invoice = crud.invoice.get(db, id=id)
+    if not invoice:
+        raise HTTPException(status_code=404, detail="Invoice not found")
+    
+    if not crud.user.is_superuser(current_user) and (
+        current_user.organization_id != invoice.organization_id
+    ):
+        raise HTTPException(status_code=400, detail="Not enough permissions")
+    
+    invoice = crud.invoice.remove(db, id=id)
+    return invoice
+
+
+@router.get("/{id}/pdf", response_class=Response)
+def generate_pdf(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Generate a PDF for the invoice.
+    """
+    invoice = crud.invoice.get(db, id=id)
+    if not invoice:
+        raise HTTPException(status_code=404, detail="Invoice not found")
+    
+    if not crud.user.is_superuser(current_user) and (
+        current_user.organization_id != invoice.organization_id
+    ):
+        raise HTTPException(status_code=400, detail="Not enough permissions")
+    
+    # Generate PDF
+    pdf_content = generate_invoice_pdf(db, invoice)
+    
+    # Return PDF as response
+    filename = f"invoice_{invoice.invoice_number}_{datetime.now().strftime('%Y%m%d')}.pdf"
+    return Response(
+        content=pdf_content,
+        media_type="application/pdf",
+        headers={"Content-Disposition": f"attachment; filename={filename}"}
+    )
--- a/app/api/v1/endpoints/organizations.py
+++ b/app/api/v1/endpoints/organizations.py
@ -0,0 +1,103 @@
+from typing import Any, List
+
+from fastapi import APIRouter, Depends, HTTPException
+from sqlalchemy.orm import Session
+
+from app import crud, models, schemas
+from app.api import deps
+
+router = APIRouter()
+
+
+@router.get("/", response_model=List[schemas.Organization])
+def read_organizations(
+    db: Session = Depends(deps.get_db),
+    skip: int = 0,
+    limit: int = 100,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Retrieve organizations.
+    """
+    if crud.user.is_superuser(current_user):
+        organizations = crud.organization.get_multi(db, skip=skip, limit=limit)
+    elif current_user.organization_id:
+        organizations = [crud.organization.get(db, id=current_user.organization_id)]
+    else:
+        organizations = []
+    return organizations
+
+
+@router.post("/", response_model=schemas.Organization)
+def create_organization(
+    *,
+    db: Session = Depends(deps.get_db),
+    organization_in: schemas.OrganizationCreate,
+    current_user: models.User = Depends(deps.get_current_active_superuser),
+) -> Any:
+    """
+    Create new organization.
+    """
+    organization = crud.organization.create(db, obj_in=organization_in)
+    return organization
+
+
+@router.get("/{id}", response_model=schemas.Organization)
+def read_organization(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Get organization by ID.
+    """
+    organization = crud.organization.get(db, id=id)
+    if not organization:
+        raise HTTPException(status_code=404, detail="Organization not found")
+    if not crud.user.is_superuser(current_user) and (
+        current_user.organization_id != id
+    ):
+        raise HTTPException(status_code=400, detail="Not enough permissions")
+    return organization
+
+
+@router.put("/{id}", response_model=schemas.Organization)
+def update_organization(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    organization_in: schemas.OrganizationUpdate,
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Update an organization.
+    """
+    organization = crud.organization.get(db, id=id)
+    if not organization:
+        raise HTTPException(status_code=404, detail="Organization not found")
+    if not crud.user.is_superuser(current_user) and (
+        current_user.organization_id != id
+    ):
+        raise HTTPException(status_code=400, detail="Not enough permissions")
+    organization = crud.organization.update(
+        db, db_obj=organization, obj_in=organization_in
+    )
+    return organization
+
+
+@router.delete("/{id}", response_model=schemas.Organization)
+def delete_organization(
+    *,
+    db: Session = Depends(deps.get_db),
+    id: int,
+    current_user: models.User = Depends(deps.get_current_active_superuser),
+) -> Any:
+    """
+    Delete an organization.
+    """
+    organization = crud.organization.get(db, id=id)
+    if not organization:
+        raise HTTPException(status_code=404, detail="Organization not found")
+    organization = crud.organization.remove(db, id=id)
+    return organization
--- a/app/api/v1/endpoints/users.py
+++ b/app/api/v1/endpoints/users.py
@ -0,0 +1,119 @@
+from typing import Any, List
+
+from fastapi import APIRouter, Body, Depends, HTTPException
+from fastapi.encoders import jsonable_encoder
+from pydantic import EmailStr
+from sqlalchemy.orm import Session
+
+from app import crud, models, schemas
+from app.api import deps
+
+router = APIRouter()
+
+
+@router.get("/", response_model=List[schemas.User])
+def read_users(
+    db: Session = Depends(deps.get_db),
+    skip: int = 0,
+    limit: int = 100,
+    current_user: models.User = Depends(deps.get_current_active_superuser),
+) -> Any:
+    """
+    Retrieve users.
+    """
+    users = crud.user.get_multi(db, skip=skip, limit=limit)
+    return users
+
+
+@router.post("/", response_model=schemas.User)
+def create_user(
+    *,
+    db: Session = Depends(deps.get_db),
+    user_in: schemas.UserCreate,
+    current_user: models.User = Depends(deps.get_current_active_superuser),
+) -> Any:
+    """
+    Create new user.
+    """
+    user = crud.user.get_by_email(db, email=user_in.email)
+    if user:
+        raise HTTPException(
+            status_code=400,
+            detail="The user with this email already exists in the system.",
+        )
+    user = crud.user.create(db, obj_in=user_in)
+    return user
+
+
+@router.put("/me", response_model=schemas.User)
+def update_user_me(
+    *,
+    db: Session = Depends(deps.get_db),
+    password: str = Body(None),
+    full_name: str = Body(None),
+    email: EmailStr = Body(None),
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Update own user.
+    """
+    current_user_data = jsonable_encoder(current_user)
+    user_in = schemas.UserUpdate(**current_user_data)
+    if password is not None:
+        user_in.password = password
+    if full_name is not None:
+        user_in.full_name = full_name
+    if email is not None:
+        user_in.email = email
+    user = crud.user.update(db, db_obj=current_user, obj_in=user_in)
+    return user
+
+
+@router.get("/me", response_model=schemas.User)
+def read_user_me(
+    current_user: models.User = Depends(deps.get_current_active_user),
+) -> Any:
+    """
+    Get current user.
+    """
+    return current_user
+
+
+@router.get("/{user_id}", response_model=schemas.User)
+def read_user_by_id(
+    user_id: int,
+    current_user: models.User = Depends(deps.get_current_active_user),
+    db: Session = Depends(deps.get_db),
+) -> Any:
+    """
+    Get a specific user by id.
+    """
+    user = crud.user.get(db, id=user_id)
+    if user == current_user:
+        return user
+    if not crud.user.is_superuser(current_user):
+        raise HTTPException(
+            status_code=400, detail="The user doesn't have enough privileges"
+        )
+    return user
+
+
+@router.put("/{user_id}", response_model=schemas.User)
+def update_user(
+    *,
+    db: Session = Depends(deps.get_db),
+    user_id: int,
+    user_in: schemas.UserUpdate,
+    current_user: models.User = Depends(deps.get_current_active_superuser),
+) -> Any:
+    """
+    Update a user.
+    """
+    user = crud.user.get(db, id=user_id)
+    if not user:
+        raise HTTPException(
+            status_code=404,
+            detail="The user with this username does not exist in the system",
+        )
+    user = crud.user.update(db, db_obj=user, obj_in=user_in)
+    return user
--- a/app/core/config.py
+++ b/app/core/config.py
@ -0,0 +1,51 @@
+from typing import List, Optional
+from pydantic import AnyHttpUrl, EmailStr, validator
+from pydantic_settings import BaseSettings
+from pathlib import Path
+
+
+class Settings(BaseSettings):
+    # Base
+    API_V1_STR: str = "/api/v1"
+    PROJECT_NAME: str = "SaaS Invoicing Application"
+    PROJECT_DESCRIPTION: str = "A SaaS invoicing application API built with FastAPI"
+    VERSION: str = "0.1.0"
+    
+    # Server configuration
+    SERVER_HOST: str = "http://localhost:8000"
+    
+    # Authentication
+    SECRET_KEY: str = "CHANGE_ME_TO_A_SECURE_RANDOM_STRING"
+    ALGORITHM: str = "HS256"
+    ACCESS_TOKEN_EXPIRE_MINUTES: int = 30
+    
+    # Database
+    DB_DIR: Path = Path("/app") / "storage" / "db"
+    SQLALCHEMY_DATABASE_URL: str = f"sqlite:///{DB_DIR}/db.sqlite"
+    
+    # CORS
+    BACKEND_CORS_ORIGINS: List[AnyHttpUrl] = []
+
+    @validator("BACKEND_CORS_ORIGINS", pre=True)
+    def assemble_cors_origins(cls, v: str | List[str]) -> List[str] | str:
+        if isinstance(v, str) and not v.startswith("["):
+            return [i.strip() for i in v.split(",")]
+        elif isinstance(v, (list, str)):
+            return v
+        raise ValueError(v)
+    
+    # Emails
+    EMAILS_ENABLED: bool = False
+    EMAILS_FROM_EMAIL: Optional[EmailStr] = None
+    EMAILS_FROM_NAME: Optional[str] = None
+    
+    # First superuser
+    FIRST_SUPERUSER_EMAIL: EmailStr = "admin@example.com"
+    FIRST_SUPERUSER_PASSWORD: str = "admin"
+
+    class Config:
+        case_sensitive = True
+        env_file = ".env"
+
+
+settings = Settings()
--- a/app/core/security.py
+++ b/app/core/security.py
@ -0,0 +1,28 @@
+from datetime import datetime, timedelta
+from typing import Any, Optional, Union
+
+from jose import jwt
+from passlib.context import CryptContext
+
+from app.core.config import settings
+
+pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")
+
+def create_access_token(
+    subject: Union[str, Any], expires_delta: Optional[timedelta] = None
+) -> str:
+    if expires_delta:
+        expire = datetime.utcnow() + expires_delta
+    else:
+        expire = datetime.utcnow() + timedelta(
+            minutes=settings.ACCESS_TOKEN_EXPIRE_MINUTES
+        )
+    to_encode = {"exp": expire, "sub": str(subject)}
+    encoded_jwt = jwt.encode(to_encode, settings.SECRET_KEY, algorithm=settings.ALGORITHM)
+    return encoded_jwt
+
+def verify_password(plain_password: str, hashed_password: str) -> bool:
+    return pwd_context.verify(plain_password, hashed_password)
+
+def get_password_hash(password: str) -> str:
+    return pwd_context.hash(password)
--- a/app/crud/init.py
+++ b/app/crud/init.py
@ -0,0 +1,6 @@
+from app.crud.crud_user import user
+from app.crud.crud_organization import organization
+from app.crud.crud_client import client
+from app.crud.crud_invoice import invoice
+
+__all__ = ["user", "organization", "client", "invoice"]
--- a/app/crud/base.py
+++ b/app/crud/base.py
@ -0,0 +1,66 @@
+from typing import Any, Dict, Generic, List, Optional, Type, TypeVar, Union
+
+from fastapi.encoders import jsonable_encoder
+from pydantic import BaseModel
+from sqlalchemy.orm import Session
+
+from app.db.base_class import Base
+
+ModelType = TypeVar("ModelType", bound=Base)
+CreateSchemaType = TypeVar("CreateSchemaType", bound=BaseModel)
+UpdateSchemaType = TypeVar("UpdateSchemaType", bound=BaseModel)
+
+
+class CRUDBase(Generic[ModelType, CreateSchemaType, UpdateSchemaType]):
+    def __init__(self, model: Type[ModelType]):
+        """
+        CRUD object with default methods to Create, Read, Update, Delete (CRUD).
+
+        **Parameters**
+
+        * `model`: A SQLAlchemy model class
+        * `schema`: A Pydantic model (schema) class
+        """
+        self.model = model
+
+    def get(self, db: Session, id: Any) -> Optional[ModelType]:
+        return db.query(self.model).filter(self.model.id == id).first()
+
+    def get_multi(
+        self, db: Session, *, skip: int = 0, limit: int = 100
+    ) -> List[ModelType]:
+        return db.query(self.model).offset(skip).limit(limit).all()
+
+    def create(self, db: Session, *, obj_in: CreateSchemaType) -> ModelType:
+        obj_in_data = jsonable_encoder(obj_in)
+        db_obj = self.model(**obj_in_data)
+        db.add(db_obj)
+        db.commit()
+        db.refresh(db_obj)
+        return db_obj
+
+    def update(
+        self,
+        db: Session,
+        *,
+        db_obj: ModelType,
+        obj_in: Union[UpdateSchemaType, Dict[str, Any]]
+    ) -> ModelType:
+        obj_data = jsonable_encoder(db_obj)
+        if isinstance(obj_in, dict):
+            update_data = obj_in
+        else:
+            update_data = obj_in.dict(exclude_unset=True)
+        for field in obj_data:
+            if field in update_data:
+                setattr(db_obj, field, update_data[field])
+        db.add(db_obj)
+        db.commit()
+        db.refresh(db_obj)
+        return db_obj
+
+    def remove(self, db: Session, *, id: int) -> ModelType:
+        obj = db.query(self.model).get(id)
+        db.delete(obj)
+        db.commit()
+        return obj
--- a/app/crud/crud_client.py
+++ b/app/crud/crud_client.py
@ -0,0 +1,10 @@
+from app.crud.base import CRUDBase
+from app.models.client import Client
+from app.schemas.client import ClientCreate, ClientUpdate
+
+
+class CRUDClient(CRUDBase[Client, ClientCreate, ClientUpdate]):
+    pass
+
+
+client = CRUDClient(Client)
--- a/app/crud/crud_invoice.py
+++ b/app/crud/crud_invoice.py
@ -0,0 +1,10 @@
+from app.crud.base import CRUDBase
+from app.models.invoice import Invoice
+from app.schemas.invoice import InvoiceCreate, InvoiceUpdate
+
+
+class CRUDInvoice(CRUDBase[Invoice, InvoiceCreate, InvoiceUpdate]):
+    pass
+
+
+invoice = CRUDInvoice(Invoice)
--- a/app/crud/crud_organization.py
+++ b/app/crud/crud_organization.py
@ -0,0 +1,10 @@
+from app.crud.base import CRUDBase
+from app.models.organization import Organization
+from app.schemas.organization import OrganizationCreate, OrganizationUpdate
+
+
+class CRUDOrganization(CRUDBase[Organization, OrganizationCreate, OrganizationUpdate]):
+    pass
+
+
+organization = CRUDOrganization(Organization)
--- a/app/crud/crud_user.py
+++ b/app/crud/crud_user.py
@ -0,0 +1,57 @@
+from typing import Any, Dict, Optional, Union
+
+from sqlalchemy.orm import Session
+
+from app.core.security import get_password_hash, verify_password
+from app.crud.base import CRUDBase
+from app.models.user import User
+from app.schemas.user import UserCreate, UserUpdate
+
+
+class CRUDUser(CRUDBase[User, UserCreate, UserUpdate]):
+    def get_by_email(self, db: Session, *, email: str) -> Optional[User]:
+        return db.query(User).filter(User.email == email).first()
+
+    def create(self, db: Session, *, obj_in: UserCreate) -> User:
+        db_obj = User(
+            email=obj_in.email,
+            hashed_password=get_password_hash(obj_in.password),
+            full_name=obj_in.full_name,
+            is_superuser=obj_in.is_superuser,
+            is_active=obj_in.is_active,
+            organization_id=obj_in.organization_id,
+        )
+        db.add(db_obj)
+        db.commit()
+        db.refresh(db_obj)
+        return db_obj
+
+    def update(
+        self, db: Session, *, db_obj: User, obj_in: Union[UserUpdate, Dict[str, Any]]
+    ) -> User:
+        if isinstance(obj_in, dict):
+            update_data = obj_in
+        else:
+            update_data = obj_in.dict(exclude_unset=True)
+        if update_data.get("password"):
+            hashed_password = get_password_hash(update_data["password"])
+            del update_data["password"]
+            update_data["hashed_password"] = hashed_password
+        return super().update(db, db_obj=db_obj, obj_in=update_data)
+
+    def authenticate(self, db: Session, *, email: str, password: str) -> Optional[User]:
+        user = self.get_by_email(db, email=email)
+        if not user:
+            return None
+        if not verify_password(password, user.hashed_password):
+            return None
+        return user
+
+    def is_active(self, user: User) -> bool:
+        return user.is_active
+
+    def is_superuser(self, user: User) -> bool:
+        return user.is_superuser
+
+
+user = CRUDUser(User)
--- a/app/db/init.py
+++ b/app/db/init.py
@ -0,0 +1,8 @@
+from app.db.base import Base  # noqa
+from app.db.session import engine, SessionLocal, get_db  # noqa
+
+# Import all the models here so that Alembic can discover them
+from app.models.user import User  # noqa
+from app.models.organization import Organization  # noqa
+from app.models.client import Client  # noqa
+from app.models.invoice import Invoice, InvoiceItem  # noqa
--- a/app/db/base.py
+++ b/app/db/base.py
@ -0,0 +1,3 @@
+from sqlalchemy.ext.declarative import declarative_base
+
+Base = declarative_base()
--- a/app/db/base_class.py
+++ b/app/db/base_class.py
@ -0,0 +1,20 @@
+from typing import Any
+from sqlalchemy import Column, Integer, DateTime
+from sqlalchemy.ext.declarative import as_declarative, declared_attr
+import datetime
+
+
+@as_declarative()
+class Base:
+    id: Any
+    __name__: str
+    
+    # Generate tablename automatically
+    @declared_attr
+    def __tablename__(cls) -> str:
+        return cls.__name__.lower()
+    
+    # Common columns for all models
+    id = Column(Integer, primary_key=True, index=True)
+    created_at = Column(DateTime, default=datetime.datetime.utcnow)
+    updated_at = Column(DateTime, default=datetime.datetime.utcnow, onupdate=datetime.datetime.utcnow)
--- a/app/db/session.py
+++ b/app/db/session.py
@ -0,0 +1,21 @@
+from sqlalchemy import create_engine
+from sqlalchemy.orm import sessionmaker
+
+from app.core.config import settings
+
+# Ensure the DB directory exists
+settings.DB_DIR.mkdir(parents=True, exist_ok=True)
+
+engine = create_engine(
+    settings.SQLALCHEMY_DATABASE_URL,
+    connect_args={"check_same_thread": False}
+)
+SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
+
+# Dependency for database session
+def get_db():
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()
--- a/app/models/init.py
+++ b/app/models/init.py
@ -0,0 +1,6 @@
+from app.models.user import User
+from app.models.organization import Organization
+from app.models.client import Client
+from app.models.invoice import Invoice, InvoiceItem
+
+__all__ = ["User", "Organization", "Client", "Invoice", "InvoiceItem"]
--- a/app/models/client.py
+++ b/app/models/client.py
@ -0,0 +1,26 @@
+from sqlalchemy import Column, String, Text, ForeignKey, Integer
+from sqlalchemy.orm import relationship
+
+from app.db.base_class import Base
+
+class Client(Base):
+    name = Column(String, index=True, nullable=False)
+    contact_name = Column(String)
+    email = Column(String)
+    phone = Column(String)
+    address = Column(Text)
+    city = Column(String)
+    state = Column(String)
+    postal_code = Column(String)
+    country = Column(String)
+    tax_id = Column(String)
+    notes = Column(Text)
+    
+    # Foreign keys
+    organization_id = Column(Integer, ForeignKey("organization.id", ondelete="CASCADE"))
+    created_by_id = Column(Integer, ForeignKey("user.id", ondelete="SET NULL"), nullable=True)
+    
+    # Relationships
+    organization = relationship("Organization", back_populates="clients")
+    created_by = relationship("User", back_populates="clients")
+    invoices = relationship("Invoice", back_populates="client")
--- a/app/models/invoice.py
+++ b/app/models/invoice.py
@ -0,0 +1,53 @@
+import enum
+from sqlalchemy import Column, String, Text, ForeignKey, Integer, Enum, Float, Date, Boolean
+from sqlalchemy.orm import relationship
+
+from app.db.base_class import Base
+
+
+class InvoiceStatus(str, enum.Enum):
+    DRAFT = "draft"
+    SENT = "sent"
+    PAID = "paid"
+    OVERDUE = "overdue"
+    CANCELLED = "cancelled"
+
+
+class Invoice(Base):
+    invoice_number = Column(String, index=True, nullable=False)
+    status = Column(Enum(InvoiceStatus), default=InvoiceStatus.DRAFT)
+    issue_date = Column(Date, nullable=False)
+    due_date = Column(Date, nullable=False)
+    subtotal = Column(Float(precision=2), nullable=False)
+    tax_rate = Column(Float(precision=2), default=0.0)
+    tax_amount = Column(Float(precision=2), default=0.0)
+    discount = Column(Float(precision=2), default=0.0)
+    total = Column(Float(precision=2), nullable=False)
+    notes = Column(Text)
+    terms = Column(Text)
+    is_recurring = Column(Boolean, default=False)
+    recurring_interval = Column(String)
+    
+    # Foreign keys
+    client_id = Column(Integer, ForeignKey("client.id", ondelete="CASCADE"))
+    organization_id = Column(Integer, ForeignKey("organization.id", ondelete="CASCADE"))
+    created_by_id = Column(Integer, ForeignKey("user.id", ondelete="SET NULL"), nullable=True)
+    
+    # Relationships
+    items = relationship("InvoiceItem", back_populates="invoice", cascade="all, delete-orphan")
+    client = relationship("Client", back_populates="invoices")
+    organization = relationship("Organization", back_populates="invoices")
+    created_by = relationship("User", back_populates="invoices")
+
+
+class InvoiceItem(Base):
+    description = Column(String, nullable=False)
+    quantity = Column(Float(precision=2), nullable=False)
+    unit_price = Column(Float(precision=2), nullable=False)
+    amount = Column(Float(precision=2), nullable=False)
+    
+    # Foreign key
+    invoice_id = Column(Integer, ForeignKey("invoice.id", ondelete="CASCADE"))
+    
+    # Relationship
+    invoice = relationship("Invoice", back_populates="items")
--- a/app/models/organization.py
+++ b/app/models/organization.py
@ -0,0 +1,22 @@
+from sqlalchemy import Column, String, Text
+from sqlalchemy.orm import relationship
+
+from app.db.base_class import Base
+
+class Organization(Base):
+    name = Column(String, index=True, nullable=False)
+    address = Column(Text)
+    city = Column(String)
+    state = Column(String)
+    postal_code = Column(String)
+    country = Column(String)
+    phone = Column(String)
+    email = Column(String)
+    website = Column(String)
+    tax_id = Column(String)
+    logo_url = Column(String)
+    
+    # Relationships
+    users = relationship("User", back_populates="organization")
+    clients = relationship("Client", back_populates="organization")
+    invoices = relationship("Invoice", back_populates="organization")
--- a/app/models/user.py
+++ b/app/models/user.py
@ -0,0 +1,21 @@
+from sqlalchemy import Boolean, Column, ForeignKey, Integer, String
+from sqlalchemy.orm import relationship
+
+from app.db.base_class import Base
+
+class User(Base):
+    email = Column(String, unique=True, index=True, nullable=False)
+    hashed_password = Column(String, nullable=False)
+    full_name = Column(String, index=True)
+    is_active = Column(Boolean, default=True)
+    is_superuser = Column(Boolean, default=False)
+    
+    # Relationship with Organization
+    organization_id = Column(Integer, ForeignKey("organization.id", ondelete="CASCADE"), nullable=True)
+    organization = relationship("Organization", back_populates="users")
+    
+    # Relationship with Invoice
+    invoices = relationship("Invoice", back_populates="created_by")
+    
+    # Relationship with Client
+    clients = relationship("Client", back_populates="created_by")
--- a/app/schemas/init.py
+++ b/app/schemas/init.py
@ -0,0 +1 @@
+# Import schemas to expose them at the package level
--- a/app/schemas/client.py
+++ b/app/schemas/client.py
@ -0,0 +1,47 @@
+from typing import Optional
+from pydantic import BaseModel, EmailStr
+
+
+# Shared properties
+class ClientBase(BaseModel):
+    name: Optional[str] = None
+    contact_name: Optional[str] = None
+    email: Optional[EmailStr] = None
+    phone: Optional[str] = None
+    address: Optional[str] = None
+    city: Optional[str] = None
+    state: Optional[str] = None
+    postal_code: Optional[str] = None
+    country: Optional[str] = None
+    tax_id: Optional[str] = None
+    notes: Optional[str] = None
+    organization_id: Optional[int] = None
+
+
+# Properties to receive via API on creation
+class ClientCreate(ClientBase):
+    name: str
+    organization_id: int
+
+
+# Properties to receive via API on update
+class ClientUpdate(ClientBase):
+    pass
+
+
+class ClientInDBBase(ClientBase):
+    id: Optional[int] = None
+    created_by_id: Optional[int] = None
+
+    class Config:
+        orm_mode = True
+
+
+# Additional properties to return via API
+class Client(ClientInDBBase):
+    pass
+
+
+# Additional properties stored in DB
+class ClientInDB(ClientInDBBase):
+    pass
--- a/app/schemas/invoice.py
+++ b/app/schemas/invoice.py
@ -0,0 +1,86 @@
+from typing import List, Optional
+from datetime import date
+from pydantic import BaseModel
+
+from app.models.invoice import InvoiceStatus
+
+
+# Invoice Item schemas
+class InvoiceItemBase(BaseModel):
+    description: Optional[str] = None
+    quantity: Optional[float] = None
+    unit_price: Optional[float] = None
+    amount: Optional[float] = None
+
+
+class InvoiceItemCreate(InvoiceItemBase):
+    description: str
+    quantity: float
+    unit_price: float
+    amount: float
+
+
+class InvoiceItemUpdate(InvoiceItemBase):
+    pass
+
+
+class InvoiceItemInDBBase(InvoiceItemBase):
+    id: Optional[int] = None
+    invoice_id: int
+
+    class Config:
+        orm_mode = True
+
+
+class InvoiceItem(InvoiceItemInDBBase):
+    pass
+
+
+# Invoice schemas
+class InvoiceBase(BaseModel):
+    invoice_number: Optional[str] = None
+    status: Optional[InvoiceStatus] = None
+    issue_date: Optional[date] = None
+    due_date: Optional[date] = None
+    subtotal: Optional[float] = None
+    tax_rate: Optional[float] = None
+    tax_amount: Optional[float] = None
+    discount: Optional[float] = None
+    total: Optional[float] = None
+    notes: Optional[str] = None
+    terms: Optional[str] = None
+    is_recurring: Optional[bool] = False
+    recurring_interval: Optional[str] = None
+    client_id: Optional[int] = None
+    organization_id: Optional[int] = None
+
+
+class InvoiceCreate(InvoiceBase):
+    invoice_number: str
+    issue_date: date
+    due_date: date
+    subtotal: float
+    total: float
+    client_id: int
+    organization_id: int
+    items: List[InvoiceItemCreate]
+
+
+class InvoiceUpdate(InvoiceBase):
+    items: Optional[List[InvoiceItemCreate]] = None
+
+
+class InvoiceInDBBase(InvoiceBase):
+    id: Optional[int] = None
+    created_by_id: Optional[int] = None
+
+    class Config:
+        orm_mode = True
+
+
+class Invoice(InvoiceInDBBase):
+    items: List[InvoiceItem] = []
+
+
+class InvoiceInDB(InvoiceInDBBase):
+    pass
--- a/app/schemas/organization.py
+++ b/app/schemas/organization.py
@ -0,0 +1,44 @@
+from typing import Optional
+from pydantic import BaseModel, EmailStr
+
+
+# Shared properties
+class OrganizationBase(BaseModel):
+    name: Optional[str] = None
+    address: Optional[str] = None
+    city: Optional[str] = None
+    state: Optional[str] = None
+    postal_code: Optional[str] = None
+    country: Optional[str] = None
+    phone: Optional[str] = None
+    email: Optional[EmailStr] = None
+    website: Optional[str] = None
+    tax_id: Optional[str] = None
+    logo_url: Optional[str] = None
+
+
+# Properties to receive via API on creation
+class OrganizationCreate(OrganizationBase):
+    name: str
+
+
+# Properties to receive via API on update
+class OrganizationUpdate(OrganizationBase):
+    pass
+
+
+class OrganizationInDBBase(OrganizationBase):
+    id: Optional[int] = None
+
+    class Config:
+        orm_mode = True
+
+
+# Additional properties to return via API
+class Organization(OrganizationInDBBase):
+    pass
+
+
+# Additional properties stored in DB
+class OrganizationInDB(OrganizationInDBBase):
+    pass
--- a/app/schemas/token.py
+++ b/app/schemas/token.py
@ -0,0 +1,11 @@
+from typing import Optional
+from pydantic import BaseModel
+
+
+class Token(BaseModel):
+    access_token: str
+    token_type: str
+
+
+class TokenPayload(BaseModel):
+    sub: Optional[int] = None
--- a/app/schemas/user.py
+++ b/app/schemas/user.py
@ -0,0 +1,39 @@
+from typing import Optional
+from pydantic import BaseModel, EmailStr
+
+
+# Shared properties
+class UserBase(BaseModel):
+    email: Optional[EmailStr] = None
+    full_name: Optional[str] = None
+    is_active: Optional[bool] = True
+    is_superuser: bool = False
+    organization_id: Optional[int] = None
+
+
+# Properties to receive via API on creation
+class UserCreate(UserBase):
+    email: EmailStr
+    password: str
+
+
+# Properties to receive via API on update
+class UserUpdate(UserBase):
+    password: Optional[str] = None
+
+
+class UserInDBBase(UserBase):
+    id: Optional[int] = None
+
+    class Config:
+        orm_mode = True
+
+
+# Additional properties to return via API
+class User(UserInDBBase):
+    pass
+
+
+# Additional properties stored in DB
+class UserInDB(UserInDBBase):
+    hashed_password: str
--- a/app/services/init.py
+++ b/app/services/init.py
@ -0,0 +1 @@
+# Service package initialization
--- a/app/services/pdf_generator.py
+++ b/app/services/pdf_generator.py
@ -0,0 +1,273 @@
+import io
+from reportlab.lib.pagesizes import letter
+from reportlab.lib import colors
+from reportlab.platypus import SimpleDocTemplate, Table, TableStyle, Paragraph, Spacer
+from reportlab.lib.styles import getSampleStyleSheet, ParagraphStyle
+from reportlab.lib.units import inch
+from sqlalchemy.orm import Session
+
+from app.models.invoice import Invoice
+
+
+def generate_invoice_pdf(db: Session, invoice: Invoice) -> bytes:
+    """
+    Generate a PDF document for an invoice.
+    
+    Args:
+        db: Database session
+        invoice: Invoice model instance
+        
+    Returns:
+        Bytes containing the PDF content
+    """
+    # Create a BytesIO buffer to receive the PDF data
+    buffer = io.BytesIO()
+    
+    # Create the PDF document using ReportLab
+    doc = SimpleDocTemplate(
+        buffer,
+        pagesize=letter,
+        rightMargin=72,
+        leftMargin=72,
+        topMargin=72,
+        bottomMargin=72
+    )
+    
+    # Container for PDF elements
+    elements = []
+    
+    # Get styles
+    styles = getSampleStyleSheet()
+    header_style = styles["Heading1"]
+    subheader_style = styles["Heading2"]
+    normal_style = styles["Normal"]
+    
+    # Custom styles
+    label_style = ParagraphStyle(
+        "label",
+        parent=normal_style,
+        fontName="Helvetica-Bold",
+        fontSize=10,
+    )
+    
+    # Add invoice header
+    elements.append(Paragraph(f"INVOICE #{invoice.invoice_number}", header_style))
+    elements.append(Spacer(1, 0.25 * inch))
+    
+    # Add organization and client information
+    org = invoice.organization
+    client = invoice.client
+    
+    # Date information
+    date_data = [
+        [Paragraph("Issue Date:", label_style), Paragraph(invoice.issue_date.strftime("%Y-%m-%d"), normal_style)],
+        [Paragraph("Due Date:", label_style), Paragraph(invoice.due_date.strftime("%Y-%m-%d"), normal_style)],
+        [Paragraph("Status:", label_style), Paragraph(invoice.status.value.upper(), normal_style)],
+    ]
+    date_table = Table(date_data, colWidths=[1.5 * inch, 2 * inch])
+    date_table.setStyle(TableStyle([
+        ("VALIGN", (0, 0), (-1, -1), "TOP"),
+        ("ALIGN", (0, 0), (0, -1), "RIGHT"),
+        ("TOPPADDING", (0, 0), (-1, -1), 1),
+        ("BOTTOMPADDING", (0, 0), (-1, -1), 1),
+    ]))
+    
+    # Organization information
+    org_data = [
+        [Paragraph("From:", label_style)],
+        [Paragraph(org.name, normal_style)],
+    ]
+    
+    if org.address:
+        org_data.append([Paragraph(org.address, normal_style)])
+    
+    city_state_zip = []
+    if org.city:
+        city_state_zip.append(org.city)
+    if org.state:
+        city_state_zip.append(org.state)
+    if org.postal_code:
+        city_state_zip.append(org.postal_code)
+    
+    if city_state_zip:
+        org_data.append([Paragraph(", ".join(city_state_zip), normal_style)])
+    
+    if org.country:
+        org_data.append([Paragraph(org.country, normal_style)])
+    
+    if org.phone:
+        org_data.append([Paragraph(f"Phone: {org.phone}", normal_style)])
+    
+    if org.email:
+        org_data.append([Paragraph(f"Email: {org.email}", normal_style)])
+    
+    if org.tax_id:
+        org_data.append([Paragraph(f"Tax ID: {org.tax_id}", normal_style)])
+    
+    org_table = Table(org_data, colWidths=[3 * inch])
+    org_table.setStyle(TableStyle([
+        ("VALIGN", (0, 0), (-1, -1), "TOP"),
+        ("TOPPADDING", (0, 0), (-1, -1), 1),
+        ("BOTTOMPADDING", (0, 0), (-1, -1), 1),
+    ]))
+    
+    # Client information
+    client_data = [
+        [Paragraph("Bill To:", label_style)],
+        [Paragraph(client.name, normal_style)],
+    ]
+    
+    if client.contact_name:
+        client_data.append([Paragraph(f"Attn: {client.contact_name}", normal_style)])
+    
+    if client.address:
+        client_data.append([Paragraph(client.address, normal_style)])
+    
+    client_city_state_zip = []
+    if client.city:
+        client_city_state_zip.append(client.city)
+    if client.state:
+        client_city_state_zip.append(client.state)
+    if client.postal_code:
+        client_city_state_zip.append(client.postal_code)
+    
+    if client_city_state_zip:
+        client_data.append([Paragraph(", ".join(client_city_state_zip), normal_style)])
+    
+    if client.country:
+        client_data.append([Paragraph(client.country, normal_style)])
+    
+    if client.email:
+        client_data.append([Paragraph(f"Email: {client.email}", normal_style)])
+    
+    if client.phone:
+        client_data.append([Paragraph(f"Phone: {client.phone}", normal_style)])
+    
+    client_table = Table(client_data, colWidths=[3 * inch])
+    client_table.setStyle(TableStyle([
+        ("VALIGN", (0, 0), (-1, -1), "TOP"),
+        ("TOPPADDING", (0, 0), (-1, -1), 1),
+        ("BOTTOMPADDING", (0, 0), (-1, -1), 1),
+    ]))
+    
+    # Combine the top tables
+    top_data = [[date_table, "", ""]]
+    top_table = Table(top_data, colWidths=[2.5 * inch, 0.5 * inch, 3 * inch])
+    elements.append(top_table)
+    elements.append(Spacer(1, 0.25 * inch))
+    
+    # Combine organization and client tables
+    address_data = [[org_table, client_table]]
+    address_table = Table(address_data, colWidths=[3 * inch, 3 * inch])
+    address_table.setStyle(TableStyle([
+        ("VALIGN", (0, 0), (-1, -1), "TOP"),
+    ]))
+    elements.append(address_table)
+    elements.append(Spacer(1, 0.5 * inch))
+    
+    # Invoice items
+    elements.append(Paragraph("Invoice Items", subheader_style))
+    elements.append(Spacer(1, 0.25 * inch))
+    
+    # Create data for the items table
+    items_data = [
+        [
+            Paragraph("Description", label_style),
+            Paragraph("Quantity", label_style),
+            Paragraph("Unit Price", label_style),
+            Paragraph("Amount", label_style),
+        ]
+    ]
+    
+    for item in invoice.items:
+        items_data.append([
+            Paragraph(item.description, normal_style),
+            Paragraph(f"{item.quantity:.2f}", normal_style),
+            Paragraph(f"${item.unit_price:.2f}", normal_style),
+            Paragraph(f"${item.amount:.2f}", normal_style),
+        ])
+    
+    # Create the items table
+    items_table = Table(items_data, colWidths=[3.5 * inch, 1 * inch, 1 * inch, 1 * inch])
+    items_table.setStyle(TableStyle([
+        ("BACKGROUND", (0, 0), (-1, 0), colors.lightgrey),
+        ("VALIGN", (0, 0), (-1, -1), "MIDDLE"),
+        ("ALIGN", (1, 0), (-1, -1), "RIGHT"),
+        ("GRID", (0, 0), (-1, -1), 0.5, colors.grey),
+        ("TOPPADDING", (0, 0), (-1, -1), 6),
+        ("BOTTOMPADDING", (0, 0), (-1, -1), 6),
+    ]))
+    elements.append(items_table)
+    elements.append(Spacer(1, 0.25 * inch))
+    
+    # Summary table (subtotal, tax, discount, total)
+    summary_data = []
+    
+    if invoice.subtotal:
+        summary_data.append([
+            "",
+            Paragraph("Subtotal:", label_style),
+            Paragraph(f"${invoice.subtotal:.2f}", normal_style),
+        ])
+    
+    if invoice.tax_rate:
+        summary_data.append([
+            "",
+            Paragraph(f"Tax ({invoice.tax_rate:.2f}%):", label_style),
+            Paragraph(f"${invoice.tax_amount:.2f}", normal_style),
+        ])
+    
+    if invoice.discount:
+        summary_data.append([
+            "",
+            Paragraph("Discount:", label_style),
+            Paragraph(f"${invoice.discount:.2f}", normal_style),
+        ])
+    
+    # Always include total
+    summary_data.append([
+        "",
+        Paragraph("Total:", ParagraphStyle(
+            "total",
+            parent=label_style,
+            fontSize=12,
+        )),
+        Paragraph(f"${invoice.total:.2f}", ParagraphStyle(
+            "total_amount",
+            parent=normal_style,
+            fontSize=12,
+            fontName="Helvetica-Bold",
+        )),
+    ])
+    
+    summary_table = Table(summary_data, colWidths=[3.5 * inch, 1.5 * inch, 1.5 * inch])
+    summary_table.setStyle(TableStyle([
+        ("VALIGN", (0, 0), (-1, -1), "MIDDLE"),
+        ("ALIGN", (1, 0), (1, -1), "RIGHT"),
+        ("ALIGN", (2, 0), (2, -1), "RIGHT"),
+        ("TOPPADDING", (0, 0), (-1, -1), 3),
+        ("BOTTOMPADDING", (0, 0), (-1, -1), 3),
+        ("LINEABOVE", (1, -1), (2, -1), 1, colors.black),
+    ]))
+    elements.append(summary_table)
+    elements.append(Spacer(1, 0.5 * inch))
+    
+    # Notes
+    if invoice.notes:
+        elements.append(Paragraph("Notes:", label_style))
+        elements.append(Paragraph(invoice.notes, normal_style))
+        elements.append(Spacer(1, 0.25 * inch))
+    
+    # Terms
+    if invoice.terms:
+        elements.append(Paragraph("Terms and Conditions:", label_style))
+        elements.append(Paragraph(invoice.terms, normal_style))
+    
+    # Build the PDF
+    doc.build(elements)
+    
+    # Get the PDF content from the buffer
+    pdf_content = buffer.getvalue()
+    buffer.close()
+    
+    return pdf_content
--- a/main.py
+++ b/main.py
@ -0,0 +1,45 @@
+import uvicorn
+from fastapi import FastAPI
+from fastapi.middleware.cors import CORSMiddleware
+
+from app.api.v1.api import api_router
+from app.core.config import settings
+
+app = FastAPI(
+    title=settings.PROJECT_NAME,
+    description=settings.PROJECT_DESCRIPTION,
+    version=settings.VERSION,
+    openapi_url="/openapi.json",
+    docs_url="/docs",
+    redoc_url="/redoc",
+)
+
+# Set up CORS middleware
+app.add_middleware(
+    CORSMiddleware,
+    allow_origins=["*"],
+    allow_credentials=True,
+    allow_methods=["*"],
+    allow_headers=["*"],
+)
+
+# Include API router
+app.include_router(api_router, prefix=settings.API_V1_STR)
+
+# Root endpoint
+@app.get("/", tags=["Root"])
+async def root():
+    return {
+        "title": settings.PROJECT_NAME,
+        "description": settings.PROJECT_DESCRIPTION,
+        "docs": f"{settings.SERVER_HOST}/docs",
+        "health": f"{settings.SERVER_HOST}/health",
+    }
+
+# Health check endpoint
+@app.get("/health", tags=["Health"])
+async def health_check():
+    return {"status": "healthy"}
+
+if __name__ == "__main__":
+    uvicorn.run("main:app", host="0.0.0.0", port=8000, reload=True)
--- a/migrations/init.py
+++ b/migrations/init.py
@ -0,0 +1 @@
+# Empty init file to make migrations a proper package
--- a/migrations/env.py
+++ b/migrations/env.py
@ -0,0 +1,83 @@
+from logging.config import fileConfig
+
+from sqlalchemy import engine_from_config
+from sqlalchemy import pool
+
+from alembic import context
+
+# Import from the application models
+from app.db.base import Base
+
+# this is the Alembic Config object, which provides
+# access to the values within the .ini file in use.
+config = context.config
+
+# Interpret the config file for Python logging.
+# This line sets up loggers basically.
+fileConfig(config.config_file_name)
+
+# add your model's MetaData object here
+# for 'autogenerate' support
+# from myapp import mymodel
+# target_metadata = mymodel.Base.metadata
+target_metadata = Base.metadata
+
+# other values from the config, defined by the needs of env.py,
+# can be acquired:
+# my_important_option = config.get_main_option("my_important_option")
+# ... etc.
+
+
+def run_migrations_offline():
+    """Run migrations in 'offline' mode.
+
+    This configures the context with just a URL
+    and not an Engine, though an Engine is acceptable
+    here as well.  By skipping the Engine creation
+    we don't even need a DBAPI to be available.
+
+    Calls to context.execute() here emit the given string to the
+    script output.
+
+    """
+    url = config.get_main_option("sqlalchemy.url")
+    context.configure(
+        url=url,
+        target_metadata=target_metadata,
+        literal_binds=True,
+        dialect_opts={"paramstyle": "named"},
+    )
+
+    with context.begin_transaction():
+        context.run_migrations()
+
+
+def run_migrations_online():
+    """Run migrations in 'online' mode.
+
+    In this scenario we need to create an Engine
+    and associate a connection with the context.
+
+    """
+    connectable = engine_from_config(
+        config.get_section(config.config_ini_section),
+        prefix="sqlalchemy.",
+        poolclass=pool.NullPool,
+    )
+
+    with connectable.connect() as connection:
+        is_sqlite = connection.dialect.name == 'sqlite'
+        context.configure(
+            connection=connection,
+            target_metadata=target_metadata,
+            render_as_batch=is_sqlite,  # Key configuration for SQLite
+        )
+
+        with context.begin_transaction():
+            context.run_migrations()
+
+
+if context.is_offline_mode():
+    run_migrations_offline()
+else:
+    run_migrations_online()
--- a/migrations/script.py.mako
+++ b/migrations/script.py.mako
@ -0,0 +1,24 @@
+"""${message}
+
+Revision ID: ${up_revision}
+Revises: ${down_revision | comma,n}
+Create Date: ${create_date}
+
+"""
+from alembic import op
+import sqlalchemy as sa
+${imports if imports else ""}
+
+# revision identifiers, used by Alembic.
+revision = ${repr(up_revision)}
+down_revision = ${repr(down_revision)}
+branch_labels = ${repr(branch_labels)}
+depends_on = ${repr(depends_on)}
+
+
+def upgrade():
+    ${upgrades if upgrades else "pass"}
+
+
+def downgrade():
+    ${downgrades if downgrades else "pass"}
--- a/migrations/versions/001_initial_tables.py
+++ b/migrations/versions/001_initial_tables.py
@ -0,0 +1,163 @@
+"""Initial tables
+
+Revision ID: 001
+Revises: 
+Create Date: 2023-12-01
+
+"""
+from alembic import op
+import sqlalchemy as sa
+import enum
+
+
+# revision identifiers, used by Alembic.
+revision = '001'
+down_revision = None
+branch_labels = None
+depends_on = None
+
+
+class InvoiceStatus(str, enum.Enum):
+    DRAFT = "draft"
+    SENT = "sent"
+    PAID = "paid"
+    OVERDUE = "overdue"
+    CANCELLED = "cancelled"
+
+
+def upgrade():
+    # Create organization table
+    op.create_table(
+        'organization',
+        sa.Column('id', sa.Integer(), nullable=False),
+        sa.Column('created_at', sa.DateTime(), nullable=True),
+        sa.Column('updated_at', sa.DateTime(), nullable=True),
+        sa.Column('name', sa.String(), nullable=False),
+        sa.Column('address', sa.Text(), nullable=True),
+        sa.Column('city', sa.String(), nullable=True),
+        sa.Column('state', sa.String(), nullable=True),
+        sa.Column('postal_code', sa.String(), nullable=True),
+        sa.Column('country', sa.String(), nullable=True),
+        sa.Column('phone', sa.String(), nullable=True),
+        sa.Column('email', sa.String(), nullable=True),
+        sa.Column('website', sa.String(), nullable=True),
+        sa.Column('tax_id', sa.String(), nullable=True),
+        sa.Column('logo_url', sa.String(), nullable=True),
+        sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_organization_id'), 'organization', ['id'], unique=False)
+    op.create_index(op.f('ix_organization_name'), 'organization', ['name'], unique=False)
+
+    # Create user table
+    op.create_table(
+        'user',
+        sa.Column('id', sa.Integer(), nullable=False),
+        sa.Column('created_at', sa.DateTime(), nullable=True),
+        sa.Column('updated_at', sa.DateTime(), nullable=True),
+        sa.Column('email', sa.String(), nullable=False),
+        sa.Column('hashed_password', sa.String(), nullable=False),
+        sa.Column('full_name', sa.String(), nullable=True),
+        sa.Column('is_active', sa.Boolean(), nullable=True),
+        sa.Column('is_superuser', sa.Boolean(), nullable=True),
+        sa.Column('organization_id', sa.Integer(), nullable=True),
+        sa.ForeignKeyConstraint(['organization_id'], ['organization.id'], ondelete='CASCADE'),
+        sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_user_email'), 'user', ['email'], unique=True)
+    op.create_index(op.f('ix_user_full_name'), 'user', ['full_name'], unique=False)
+    op.create_index(op.f('ix_user_id'), 'user', ['id'], unique=False)
+
+    # Create client table
+    op.create_table(
+        'client',
+        sa.Column('id', sa.Integer(), nullable=False),
+        sa.Column('created_at', sa.DateTime(), nullable=True),
+        sa.Column('updated_at', sa.DateTime(), nullable=True),
+        sa.Column('name', sa.String(), nullable=False),
+        sa.Column('contact_name', sa.String(), nullable=True),
+        sa.Column('email', sa.String(), nullable=True),
+        sa.Column('phone', sa.String(), nullable=True),
+        sa.Column('address', sa.Text(), nullable=True),
+        sa.Column('city', sa.String(), nullable=True),
+        sa.Column('state', sa.String(), nullable=True),
+        sa.Column('postal_code', sa.String(), nullable=True),
+        sa.Column('country', sa.String(), nullable=True),
+        sa.Column('tax_id', sa.String(), nullable=True),
+        sa.Column('notes', sa.Text(), nullable=True),
+        sa.Column('organization_id', sa.Integer(), nullable=False),
+        sa.Column('created_by_id', sa.Integer(), nullable=True),
+        sa.ForeignKeyConstraint(['created_by_id'], ['user.id'], ondelete='SET NULL'),
+        sa.ForeignKeyConstraint(['organization_id'], ['organization.id'], ondelete='CASCADE'),
+        sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_client_id'), 'client', ['id'], unique=False)
+    op.create_index(op.f('ix_client_name'), 'client', ['name'], unique=False)
+
+    # Create invoice table
+    op.create_table(
+        'invoice',
+        sa.Column('id', sa.Integer(), nullable=False),
+        sa.Column('created_at', sa.DateTime(), nullable=True),
+        sa.Column('updated_at', sa.DateTime(), nullable=True),
+        sa.Column('invoice_number', sa.String(), nullable=False),
+        sa.Column('status', sa.Enum('draft', 'sent', 'paid', 'overdue', 'cancelled', name='invoicestatus'), nullable=True),
+        sa.Column('issue_date', sa.Date(), nullable=False),
+        sa.Column('due_date', sa.Date(), nullable=False),
+        sa.Column('subtotal', sa.Float(precision=2), nullable=False),
+        sa.Column('tax_rate', sa.Float(precision=2), nullable=True),
+        sa.Column('tax_amount', sa.Float(precision=2), nullable=True),
+        sa.Column('discount', sa.Float(precision=2), nullable=True),
+        sa.Column('total', sa.Float(precision=2), nullable=False),
+        sa.Column('notes', sa.Text(), nullable=True),
+        sa.Column('terms', sa.Text(), nullable=True),
+        sa.Column('is_recurring', sa.Boolean(), nullable=True),
+        sa.Column('recurring_interval', sa.String(), nullable=True),
+        sa.Column('client_id', sa.Integer(), nullable=False),
+        sa.Column('organization_id', sa.Integer(), nullable=False),
+        sa.Column('created_by_id', sa.Integer(), nullable=True),
+        sa.ForeignKeyConstraint(['client_id'], ['client.id'], ondelete='CASCADE'),
+        sa.ForeignKeyConstraint(['created_by_id'], ['user.id'], ondelete='SET NULL'),
+        sa.ForeignKeyConstraint(['organization_id'], ['organization.id'], ondelete='CASCADE'),
+        sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_invoice_id'), 'invoice', ['id'], unique=False)
+    op.create_index(op.f('ix_invoice_invoice_number'), 'invoice', ['invoice_number'], unique=False)
+
+    # Create invoice_item table
+    op.create_table(
+        'invoiceitem',
+        sa.Column('id', sa.Integer(), nullable=False),
+        sa.Column('created_at', sa.DateTime(), nullable=True),
+        sa.Column('updated_at', sa.DateTime(), nullable=True),
+        sa.Column('description', sa.String(), nullable=False),
+        sa.Column('quantity', sa.Float(precision=2), nullable=False),
+        sa.Column('unit_price', sa.Float(precision=2), nullable=False),
+        sa.Column('amount', sa.Float(precision=2), nullable=False),
+        sa.Column('invoice_id', sa.Integer(), nullable=False),
+        sa.ForeignKeyConstraint(['invoice_id'], ['invoice.id'], ondelete='CASCADE'),
+        sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_invoiceitem_id'), 'invoiceitem', ['id'], unique=False)
+
+
+def downgrade():
+    # Drop tables in reverse order
+    op.drop_index(op.f('ix_invoiceitem_id'), table_name='invoiceitem')
+    op.drop_table('invoiceitem')
+    
+    op.drop_index(op.f('ix_invoice_invoice_number'), table_name='invoice')
+    op.drop_index(op.f('ix_invoice_id'), table_name='invoice')
+    op.drop_table('invoice')
+    
+    op.drop_index(op.f('ix_client_name'), table_name='client')
+    op.drop_index(op.f('ix_client_id'), table_name='client')
+    op.drop_table('client')
+    
+    op.drop_index(op.f('ix_user_id'), table_name='user')
+    op.drop_index(op.f('ix_user_full_name'), table_name='user')
+    op.drop_index(op.f('ix_user_email'), table_name='user')
+    op.drop_table('user')
+    
+    op.drop_index(op.f('ix_organization_name'), table_name='organization')
+    op.drop_index(op.f('ix_organization_id'), table_name='organization')
+    op.drop_table('organization')
--- a/requirements.txt
+++ b/requirements.txt
@ -0,0 +1,15 @@
+fastapi==0.105.0
+uvicorn==0.24.0
+sqlalchemy==2.0.23
+alembic==1.13.0
+pydantic==2.5.2
+pydantic-settings==2.1.0
+pydantic[email]==2.5.2
+python-jose[cryptography]==3.3.0
+passlib[bcrypt]==1.7.4
+python-multipart==0.0.6
+reportlab==4.0.7
+email-validator==2.1.0.post1
+ruff==0.1.6
+pytest==7.4.3
+httpx==0.25.2
				`@ -0,0 +1 @@`
				`# Import schemas to expose them at the package level`
				`@ -0,0 +1 @@`
				`# Empty init file to make migrations a proper package`