Support removal of KB credentials entry by following endpoint:
More details can be found in the dedicated section of "Spike: MODKBEKBJ-390 - describe design for "Single tenant multiple EBSCO KBs" scenario"
- existing KB credentials entry can be removed by id
- if there are related records (like users) return an error
- the endpoint created and works according to the requirements
- the endpoint is covered with unit tests
- API tests added to cover endpoint functionality