Is it possible to using gRPC over message broker?

Like [this](https://github.com/awakesecurity/grpc-mqtt).

This is useful if the client and server are behind different firewalls.

I have checked out Server::serve_with_incoming, it required , so it might work.

```rust
pub async fn serve_with_incoming(
self,
incoming: I,
) -> Result<(), super::Error>
where
I: Stream>,
IO: AsyncRead + AsyncWrite + Connected + Unpin + Send + 'static,
IO::ConnectInfo: Clone + Send + Sync + 'static,
IE: Into,
L: Layer,
L::Service: Service, Response = Response> + Clone + Send + 'static,
<>::Service as Service>>::Future: Send + 'static,
<>::Service as Service>>::Error: Into + Send,
ResBody: http_body::Body + Send + 'static,
ResBody::Error: Into,
{

```
But for the generated client-side it requests an *Endpoint*, which is linked directly to http2.
```rust
#[tokio::main]
async fn main() -> Result<(), Box> {
let mut client = EchoClient::connect("http://[::1]:50051").await.unwrap();

```

Is this possible?