* 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.
* 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.