[KajMagnus]

> "Don't know why this is necessary"

Ok so the other replies here clarify why — but really it'd have been nice if there was at least some consistent interface between all the OAuth / OIDC providers, so one wouldn't need to learn new interfaces all the time.

... And, worse, now I need to take screenshots and document all these different interfaces, for an open source project I'm building, whose users might want to register OIDC client apps too. :- /