Now that the code is public, having a hardcoded string seems even less
prudent...

There are no more updates available as of now.

Login still works regardless of case!

Required by the more languages team.

When talks are removed from Fahrplan, move them to a dummy stage.

This fixes a problem when updating the profile due to having a hidden email field.

This allows signup, profile edits and login/logout.
Note that due to poor naming, there are conflicts between our session
model und what devise thinks a session should be. In particular, we have
to rename `new_session_path(resource_name)` -> `new_user_session_path`
and `session_path(resource_name)` -> `user_session_path`.

Cf. https://github.com/heartcombo/devise/issues/2800