... when the user is destroyed.
1. Normally, for a given awardable and award emoji name, a user is only allowed
to create a single award emoji.
2. This validation needs to be removed for ghost users, since:
- User A and User B have created award emoji - with the same name and against
the same awardable
- User A is deleted. Their award emoji is moved to the ghost user
- User B is deleted. Their award emoji needs to be moved to the ghost user.
However, this breaks the uniqueness validation, since the ghost user is
only allowed to have one award emoji of a given name for a given awardable
