* Introduce Superadmin field in OAuthClient configuration
* Implement IsSuperadmin method in OAuthRegistry
* Update identityAdmin to check superadmin status via OAuthRegistry
* Add tests for OAuthRegistry superadmin functionality
- Add OAuth 2.0 support with authorization code flow and dynamic client registration.
- Introduce new handlers for OAuth metadata, client registration, authorization, and token issuance.
- Enhance authentication middleware to support OAuth client credentials.
- Create in-memory stores for authorization codes and tokens.
- Update configuration to include OAuth client details.
- Ensure validation checks for OAuth clients in the configuration.
warkanum