Serving Ontop of Abstract Transport

### Is your feature request related to a problem? Please describe.
I need to organize a gRPC communication among services on transport agnostic basis

### Describe the solution you'd like
I'd like to be able to serve an instance (server or client) based on regular `Duplex` stream without explicit ports binding (something similar to golang [Listener](https://github.com/grpc/grpc-go/blob/3e7b97febc7fa0d9804786b60c4de14d700c6956/server.go#L747) or [Connection](https://github.com/grpc/grpc-go/blob/3e7b97febc7fa0d9804786b60c4de14d700c6956/server.go#L840) injection)

### Describe alternatives you've considered
As I understand the current implementation tightly depends on internally created HTT2 server instance. So if the desired behavior Is not an. option I can see the only way to reimplement some simpler analog just taking advantage solely of `Potobuf` it self only.

I'm not sure maybe this is not obvious from implementation and there's a chance just to use some lower level classes from the library to achieve this?
Or is there any minimal changes I can change/extend the codebase locally to get the behavior?

Please advice the most relevant solution in my case.

Thank you