[rest_gateway] Enhanced logging and error handling for gRPC gateway initialization

[ramonfigueiredo]

• Added log messages for JWT validation, gRPC handler registration, and other rest_gateways logs
• Modified jwtMiddleware to log successful token validation and access requests
• Refactored gRPC handler registration into a centralized function
  • Created registerGRPCHandlers function to streamline and consolidate the registration of multiple gRPC service handlers
  • Simplified code structure by using a loop to register each handler, improving maintainability and readability
  • Added logging for individual handler registration success and errors to facilitate debugging