Implement RPC feature

[bcherry]

Pretty much identical to livekit/client-sdk-android#578

I included tests which mock the underlying data channel sending and receiving to test both sides in the same SDK app instance.

[hiroshihorie]

✅ Looks good !
Applied format & moved code to a separate file (extension) to organize.

Was just wondering if the Public APIs are "Swifty" enough 🧐

[bcherry]

Was just wondering if the Public APIs are "Swifty" enough 🧐

I could make it more swifty like this: register(rpcMethod:"hello") { data in } and perform(rpcMethod: "hello", on: "some-identity", payload: "xxx", timeout: 8)?

Only downside is it loses consistency with other sdks in parameter structure. i was also thinking that maybe it would be better to revise across all SDKs to a separate construct attached to room e.g. room.rpc.register("xxx") { _ in } and room.rpc.perform("xxx", on: "yyy")

[bcherry]

Was just wondering if the Public APIs are "Swifty" enough 🧐

I could make it more swifty like this: register(rpcMethod:"hello") { data in } and perform(rpcMethod: "hello", on: "some-identity", payload: "xxx", timeout: 8)?

Only downside is it loses consistency with other sdks in parameter structure. i was also thinking that maybe it would be better to revise across all SDKs to a separate construct attached to room e.g. room.rpc.register("xxx") { _ in } and room.rpc.perform("xxx", on: "yyy")

@hiroshihorie I made those changes then reverted them while writing the docs because the way the docs are written it really is a lot nicer if all platforms have the same method names