fix: remove own partner from partner/all endpoint

[eschrewe]

Description

• added filter to exclude own partner entity from output in GET partner/all endpoint
• solves Partner dialogs list also ourself #524
• solves Catalogue View: I can select my own company as a partner  #423

Pre-review checks

Please ensure to do as many of the following checks as possible, before asking for committer review:

• DEPENDENCIES are up-to-date. Dash license tool. Committers can open IP issues for restricted libs.
• Copyright and license header are present on all affected files
• If helm chart has been changed, the chart version has been bumped to either next major, minor or patch level (compared to released chart).

[tom-rm-meyer-ISST]

Thanks a lot!