Comment # 19 on bug 83396 from Patrick Ohly

(In reply to comment #17)
> Created attachment 105956 [details] [review] [review]
> new oauth2 backend
> 
> OAuth2 backend now install provideroauth2.so

That's only one part of what I wondered about. There's also USE_REFRESH_TOKEN,
enble_refresh_token and last but not least, the "username=refresh-token:"
prefix.

Let me propose a different patch...