code: public GrpcServerBuilder addService(ServiceType serviceType, GrpcService serviceDefinition) {
      mServices.add(serviceType);
      return addService(serviceDefinition);
    }
docs: Add a service to this server.
  
  @param serviceType the type of service
  @param serviceDefinition the service definition of new service
  @return an updated instance of this {@link GrpcServerBuilder}