```html Authentication API Documentation

Authentication API Documentation

Authentication Endpoints

Login

Endpoint: /api/v1/auth/login

Method: POST

Description: Authenticates a user and returns an access token.

Request Body (JSON):

{ "username": "string", "password": "string" }

Response (JSON - Successful):

{ "access_token": "string", "user_id": "integer" }

Response (JSON - Error):

{ "error": "string" }

Register

Endpoint: /api/v1/auth/register

Method: POST

Description: Registers a new user.

Request Body (JSON):

{ "username": "string", "password": "string", "email": "string" }

Response (JSON - Successful):

{ "user_id": "integer", "message": "User created successfully" }

Response (JSON - Error):

{ "error": "string" }

Refresh Token

Endpoint: /api/v1/auth/refresh

Method: POST

Description: Refreshes an existing access token using a refresh token.

Request Body (JSON):

{ "refresh_token": "string" }

Response (JSON - Successful):

{ "access_token": "string" }

Response (JSON - Error):

{ "error": "string" }
```