server/v2: wire grpc and gateway

[tac0turtle]

• wire grpc (See feat: wire new handlers to grpc #22333)
• wire gateway for querying (See feat(server/v2/grpcgateway): register grpcgateway server and module endpoints #22701)

[julienrbrt]

ref: https://github.com/cosmos/cosmos-sdk/pull/22278/files#diff-37832b152aeffcb6b1aa5704837f3fa357876b1993277b3657722863192f3f83R123

[julienrbrt]

Wouldn't we able to use the rest v2 (post endpoint) server, and proxy query to it?
Basically, an http handler that split the request path, and checks the proto registry matching Service, and make Post a request from the server for it?

That will be hacky, but does sound possible. That will be probably less efficient than the new rest endpoint, but will be good enough for those willing backward compat.

[julienrbrt]

Given that #22701 did the wiring, closing this as completed.
I'll create another issue with the way we wanted to do it