Add tests

Created by: joshuai96

As mentioned in SovereignCloudStack/issues#222 the API server should be tested by unit oder behavior testing.

These test use a mocked SQL connection and fake http requests, to test the API operation handlers, as if they were called by a client.

The mocked SQL connections is used to simulated any kind of data or error returned by the databse and checks Gorms query generation against a expected query.

The fake http requests deliver request bodies to the function.

A request recorder checks for the http response, if any.