- Added FirebaseAuth struct and TokenVerifier interface for verifying Firebase ID tokens.
- Introduced FirebaseConfig struct in config to manage Firebase credentials and project ID.
- Implemented OAuth handler for Firebase ID token verification in HTTP handlers.
- Added middleware for authenticating requests using Firebase tokens.
- Updated router to conditionally apply authentication based on configuration.
- Created tests for the new authentication middleware.
- Added request and response types for Firebase OAuth handling.
- Included a sample JSON file for testing purposes.
