#1 Use signal instead of view logic
requested to merge feat/1-later-promoted-teamcaptains-coordinator-should-be-auto-verified-for-already-joined-events-pt2 into develop
The functionality of promiting users should also be possible in the backend.
see https://gitlab.die-linke.de/die-linke-app/die-linke-app-service/-/issues/1#note_853