Revert "controllers/base: Removed obsolete identity handling code"

This reverts commit 237f538970cc5d44456c3556d12da6f779a2c856.

Turns out this is useful when the user decides to change his email address.
In that scenario the identity dict will be {} which is True-ish but there
will be no information inside. Until there is a better solution we log the
user out in such cases.
AUTHORS: Added missing translators