Update README to document username-based authentication

README.md

@@ -8,7 +8,7 @@ A full-featured e-commerce API built with FastAPI and SQLite.
 - **Product Management**: Products with categories, pricing, and inventory management
 - **Shopping Cart**: Add, update, remove items in user's shopping cart
 - **Order Processing**: Create orders from cart, track order status
-- **Authentication**: JWT-based authentication with role-based access control
+- **Authentication**: Username-based JWT authentication with role-based access control
 
 ## Tech Stack
 
@@ -23,8 +23,8 @@ A full-featured e-commerce API built with FastAPI and SQLite.
 
 ### Authentication
 
-- `POST /api/v1/auth/login`: Login and get access token
-- `POST /api/v1/auth/register`: Register a new user
+- `POST /api/v1/auth/login`: Login with username and password to get access token
+- `POST /api/v1/auth/register`: Register a new user (requires username, email, and password)
 - `GET /api/v1/auth/me`: Get current user information
 
 ### Users
@@ -104,6 +104,13 @@ uvicorn main:app --reload
 
 The API will be available at http://localhost:8000.
 
+### Authentication Note
+
+This API uses username-based authentication rather than email-based. When registering and logging in:
+- Username is the primary identifier for authentication
+- Email is still required during registration but is not used for login
+- Password must meet security requirements (minimum 8 characters)
+
 ## Documentation
 
 FastAPI provides automatic API documentation:
@@ -124,6 +131,10 @@ Apply migrations:
 alembic upgrade head
 ```
 
+#### Recent Migrations
+
+- **2a3b4c5d6e7f_add_username_field**: Added username field to User model and migrated from email-based to username-based authentication
+
 ### Running Tests
 
 ```bash