Using Grpc protocol in the router to communicate with the federated services

[mostafao-spotify]

Is your feature request related to a problem? Please describe.

We use in my company the Grpc protocol to communicate between the micro-services but the router supports only http.

Describe the solution you'd like

So I was curious if there are any future plans to enable the GRPC Protocol for the router image communication between services in addition to the Http protocol currently used through a configuration maybe?

Describe alternatives you've considered

we're using an adapter service to do the conversion, but of course this adds to the latency.

[vanthome]

We also have such a use case, that would be really nice if apollo router can support this.