test: add integration test for exception handling

Motivation:

The exception handling currently has no test.

Modification:

Add integration tests to make sure that the exceptions were thrown when and where they were suppose. This is done by simulating various scenarios and mocking the server behaviour.

Result:

Improve test coverage for exception handling

Documentation:

To run the test, first get the Helmholtz AAI token and add it the mvn command as shown to compile and run the tests: mvn -Dtoken= test|package|install To skip the tests, simply run: mvn -DskipTests package|install

Target: master Acked-by: Review: https://gitlab.hzdr.de/hifis-technical-platform/helmholtz-cerebrum/-/merge_requests/19