* Implement TwoFactorAuthenticator for 2FA login.
* Create DatabaseTwoFactorProvider for PostgreSQL integration.
* Add MemoryTwoFactorProvider for in-memory testing.
* Develop TOTPGenerator for generating and validating codes.
* Include tests for all new functionalities.
* Ensure backup codes are securely hashed and validated.
* Introduce OAuth2 authentication examples for Google, GitHub, and custom providers.
* Implement OAuth2 methods for handling authentication, token refresh, and logout.
* Create a flexible structure for supporting multiple OAuth2 providers.
* Enhance DatabaseAuthenticator to manage OAuth2 sessions and user creation.
* Add database schema setup for OAuth2 user and session management.
* Implemented resolvespec_register stored procedure for user registration.
* Added RegisterRequest struct for registration data.
* Created Register method in DatabaseAuthenticator.
* Updated tests for successful registration and error handling for duplicate usernames and emails.
