revoking consent when proxying auth to other IDP

[Cantor, Scott]

> Actually I would say this needs to be put on
> https://idp.example.org/idp/profile/user/prefs

That page is really just a client side thing, it doesn't do anything but run some Javascript to manage some cookies and is sort of orphaned at this point, it's mostly just an example of a user flow. It's not updateable at upgrade time for example, which disqualifies it from exposing actual functionality we have to support.

It could be rebuilt of course, but since somebody else is already working on a general replacement, that's a more obvious starting point.

-- Scott