Add basic infrastructure to test REST API
Architecture - Internal libs
We must toroughly and exaustively test Rudder API, because we must be 100% sure about what exactly is returned, and that these things don't change appart in a control and documented way.
And it's easy to do so (contrary to testing UI, or even other statefull part of the app).
This ticket is just here to set-up the infrastructure to test API. It can be see as an "hello world" for that, and will certainly not be sufficient to do anything complexe - but at least, the main process of "build a lift app -> build a request -> use the request -> check the result" will be working.