Add Koala Authentication

[ArondenOuden]

Koala Authentication was already present, but it needs to be turned on and connected to the koala oauth

[SamStaijen]

if you want a cheet sheet of how to implement koala auth in python, https://github.com/svsticky/sturdy-memory/pull/4/files might help :). Have yet to properly document it, but the MVP is there, and using only the discovery url, one is able to login. If the merge request does not exist anymore, it is probably visible on develop branch. Specifically, look at the backend/auth folder. this endpoint does the login thingies