SPIKE: investigate Karate for building integration tests

The ticket is created in Okapi but let's discuss if a smaller module like mod-authtoken is a better starting point.

A reservation has been raised during standup about the plan to keep Karate API integration tests in a single repo. We discussed that this might be a deal breaker for the platform projects like Okapi.

Investigate:

• review Karate API integration testing framework and compare to RestAssured which is currently used by Okapi and RMB
• analyse if the tests can be kept in individual repos instead