Add tests for permission managment

https://gitlab.hzdr.de/hub-terra/sms/backend/-/merge_requests/265#note_1335586

TODOs:

• test of patch for internal configuration & user with group permission
• test of patch for an internal configuration & user without group permission
• test of patch for an internal configuration & superuser
• detail view patch & delete with mocking IDL calls

I think we can combine those also with the tests for public configurations - as the logic and the results should be the very same (users with groups & superuser can, others can't).

For the delete requests, we need those as well. Maybe here also with the case of a user that is in the group as member but not as admin.

Maybe use: https://docs.python.org/3/library/unittest.mock.html