Develop a prototype for authentication

Description

We should develop a prototype that shows how the authentication could work for one university and one authentication provider to get started in this whole subject of developing a generic solution for all universities.

Further information (only accessable with a login at the Technical University of Berlin):
https://gitlab.tubit.tu-berlin.de/stapps/projectmanagement/issues/22
https://gitlab.tubit.tu-berlin.de/stapps/backend/issues/190

cc: @krlwlfrt