feat: Implement OAuth2 authentication with Google and GitHub

- Added OAuth2 endpoints for Google and GitHub authentication.
- Created OAuth service to handle provider interactions and user info retrieval.
- Implemented user OAuth repository for managing user OAuth links in the database.
- Updated auth service to support linking existing users and creating new users via OAuth.
- Added CORS middleware to allow frontend access.
- Created tests for OAuth endpoints and service functionality.
- Introduced environment configuration for OAuth client IDs and secrets.
- Added logging for OAuth operations and error handling.

app/api/v1/__init__.py

@@ -2,7 +2,7 @@
 
 from fastapi import APIRouter
 
-from app.api.v1 import auth, main
+from app.api.v1 import auth, main, oauth
 
 # V1 API router with v1 prefix
 api_router = APIRouter(prefix="/v1")
@@ -10,3 +10,4 @@ api_router = APIRouter(prefix="/v1")
 # Include all route modules
 api_router.include_router(main.router, tags=["main"])
 api_router.include_router(auth.router, prefix="/auth", tags=["authentication"])
+api_router.include_router(oauth.router, prefix="/oauth", tags=["oauth"])