feat(auth): integrate OAuth authentication and introspection support

- Updated HttpStreamTransportConfig to use AuthConfig and CORSConfig types.
- Enhanced SSEServerTransport to handle OAuth metadata and introspection endpoints.
- Added ProtectedResourceMetadata class for managing OAuth protected resource metadata.
- Implemented tests for ProtectedResourceMetadata, OAuthAuthProvider, JWTValidator, and IntrospectionValidator.
- Created MockAuthServer for simulating authentication server behavior in tests.
- Added caching mechanism for introspection results to improve performance.
- Validated required claims and token expiration in introspection and JWT validation tests.

Author: jmrobles