Motivation:

User belonging to known Helmholtz organisation can create
and be part of a management team to manage a marketplace
service. This patch introduce the code to model this
relationship and expose it usage through the restful API.

Modification:

- create a relationship class for "MANAGES" called Management.
- provide the ability to add and delete the relationship. Hence,
    the market-service controller expose the api, the service
    provide the bridge between the api and the repository. The
    repository contain the neccessary query to interact with
    the database.
- fix minor typo inside the market-service-controller,
    market-service-service and market-service-repository class
- overide both the equals and hashCode method of the
    market-service class

Result:

MANAGES relationship can now be added and deleted through the
restful api.

Target: master
Review-at: https://gitlab.hzdr.de/hifis-technical-platform/helmholtz-cerebrum/-/merge_requests/33