- Add OAuthServer for handling OAuth2 flows including authorization, token exchange, and client registration.
- Introduce DatabaseAuthenticator for persisting clients and authorization codes.
- Implement SQL procedures for client registration, code saving, and token introspection.
- Support for external OAuth2 providers and PKCE (Proof Key for Code Exchange).
* Introduce SQLNames struct to define stored procedure names.
* Update DatabaseAuthenticator, JWTAuthenticator, and other providers to use SQLNames for procedure calls.
* Remove hardcoded procedure names for better flexibility and customization.
* Implement validation for SQL names to ensure they are valid identifiers.
* Add tests for SQLNames functionality and merging behavior.