Add a function email_allowed_for_realm that checks whether a user with
given email is allowed to join a given realm (either because the email
has the right domain, or because the realm is open), and use it
whenever deciding whether to allow adding a user to a realm.
This commit is not intended to change any behavior, except in one case
where the Zulip realm's domain was not being converted to lowercase.
This needs to be deployed to both staging and prod at the same
off-peak time (and the schema migration run).
At the time it is deployed, we need to make a few changes directly in
the database:
(1) UPDATE django_content_type set app_label='zerver' where app_label='zephyr';
(2) UPDATE south_migrationhistory set app_name='zerver' where app_name='zephyr';
(imported from commit eb3fd719571740189514ef0b884738cb30df1320)
Sahil Dua
Tim Abbott
Reid Barton
Jessica McKellar
Tim Abbott