Macro declare_rpc

macro_rules! declare_rpc {
    ($service:ty, $m_input:ty, $m_output:ty) => { ... };
}

Declare a message to be a rpc message for a service.

Example:

declare_rpc!(TestService, TestRequest, TestResponse);

This is equivalent to:

impl RpcMsg<TestService> for TestRequest {
   type Response = TestResponse;
}