Add user update via e-mail callback

Require a user to login after a certain time, if the home org doesn't allow for backchannel user updates.

assigned to @michael.simon

created branch feature/ISSUE-206_add-user-update-via-e-mail-callback to address this issue

mentioned in merge request !84 (merged)

mentioned in commit 771568a7

closed with merge request !84 (merged)