Motivation:

The Cerebrum API controllers have the same structure and design
implementation. This leads to quite a number of code dublications.

Modification:

- decouple the service code from the controllers and create a
    service per controller
- create an inteface for the cerebrum's controllers service
- create a common base class for all the services.
- adjust the controller to use its corresponding service
- add tests to check the unchecked part of the base service class
- create a new method called checkUuidValidity to the
    CerebrumEntityUuidGenerator class. This method will throw
    an exception if uuid is invalid.

Result:

Reduce dublication from 1.7% to 0%  and increase code maintainability.

Target: master
Review-at: https://gitlab.hzdr.de/hifis-technical-platform/helmholtz-cerebrum/-/merge_requests/28