CI/CD for server backend

[PGijsbers]

Server testing currently happens indirectly by users or connector package maintainers. This "burden" should be shifted back to the server development team with a proper CI/CD pipeline. This issue could further be split into a test suite which tests the server internals, and a test suite which tests that the API responses remain correct (this also helps server devs know when to communicate important changes to the connector devs).

This will (in part) be addressed by making sure the functionalities to be rebuilt in Python are covered by tests.