Make test responses related to groups realistic for respective authenticator class

[consideRatio]

We currently just inject groups=["group1"] in the user model we mock in tests, but maybe there is a groups property that we can get named something else etc - it could be nice to mock like that instead.

In practice, I see resolving this issue meaning to look into various authenticator classes associated identity providers userinfo responses looking for data associated with group membership of some kind (and then updating tests to include such data in the mocked response).

One could also consider setting a default value, but let's not track that as part of this narrowly scoped issue.