feat: add GrpcMethod extension into request for client

[linw1995]

Motivation

The request was added with the GrpcMethod extension in the gRPC client code generated on tonic-build, for this reason, we can inspect the gRPC method info within the client interceptor function. In the future, this feature could be used for supporting Prometheus middleware metrics on a common basis.

    fn client_intercept(req: Request<()>) -> Result<Request<()>, Status> {
        println!("Intercepting client request: {:?}", req);

        let gm = req.extensions().get::<GrpcMethod>().unwrap();
        assert_eq!(gm.service(), "test.Test");
        assert_eq!(gm.method(), "UnaryCall");

        Ok(req)
    }
    let mut client = TestClient::with_interceptor(channel, client_intercept);
    client.unary_call(Request::new(Input {})).await.unwrap();

Solution

Update tonic-build to generate client-side codes that support the GrpcMethod extension. Why not review the code changes in this file, tonic-health/src/generated/grpc.health.v1.rs, to see the differences? 😄

[LucioFranco]

Everything looks good, have one more request then we can merge.

[LucioFranco]

Thanks for following through on this!