public GrpcServiceBuilder addService(ServerServiceDefinition service) {
        registryBuilder.addService(requireNonNull(service, "service"), null, ImmutableList.of());
        return this;
    }
Adds a gRPC {@link ServerServiceDefinition} to this {@link GrpcServiceBuilder}, such as
what's returned by {@link BindableService#bindService()}.
grpc/src/main/java/com/linecorp/armeria/server/grpc/GrpcServiceBuilder.java