- Extend `users_o` and `subusers_o` with `two_factor_enabled` and `two_factor_secret` properties.
- Implement methods for managing 2FA (`isTwoFactorEnabled`, `setTwoFactorSecret`, `verify_2fa_code`) in authentication logic.
- Add 2FA handling in login flows for both users and subusers, including token generation and validation.
- Introduce `totp` class for TOTP-based authentication, including QR code generation and code verification.
- Add test cases for 2FA functionality (`TwoFactorAuthTest.php`) and coverage for login scenarios with 2FA.
- Update OpenAPI specifications to include 2FA flows (`auth/2fa/setup`, `auth/2fa/enable`, `auth/2fa/verify`, `auth/2fa/disable`).