Refactoring of test system and alternative API testing

Description: The test system needs to be refactored and split up to speed up testing processes with the already existing docker container. Tests need to be split up in more sections/test suits so that we can execute them in parallel using our docker container The underlying FeatureContextFiles need to be refactored, cleaned, adapted where necessary and code duplications need to be removed Since we are on our way to introduce APIv2, it is a good time to check if our current Testsuite (Behat) is adequately equipped to extensively test our new API. If not an alternative should be found and implemented (in accordance with the rest of the team)