* FIX: Ensure the same email cannot be invited twice
When creating a new invite with a duplicated email, the old invite will
be updated and returned. When updating an invite with a duplicated email
address, an error will be returned.
* FIX: not Ember helper does not exist
* FIX: Sync can_invite_to_forum? and can_invite_to?
The two methods should perform the same basic set of checks, such as
check must_approve_users site setting.
Ideally, one of the methods would call the other one or be merged and
that will happen in the future.
* FIX: Show invite to group if user is group owner
60be1556fc