Improve documentation and tooling around integration testing of services

[jorgecarleitao]

Feature Request

Crates

tonic

Motivation

It is currently a bit unclear to me how client-server should be tested in integration. E.g. what should an implementation of

fn test_helper(message: FooRequest, expected: Vec<FooResponse>)

be to test a specific server-client of one of the services?

Proposal

Add an example (and potentially helper methods) to make it easy to write tests.

Alternatives

Leave it as is