Here's a crazy scenario: user1 has a single-character key for Character One; user2 has a single-character key for Character Two; user3 has a full-account key covering both Character One and Character Two (and since this key has duplicate character, this key gets violation=True). Merging user2 and user3 shouldn't automatically unset the violation on the key, since there's still a conflict with user1.

We may also potentially want to clear violations on the first user's credentials (if the keys were added in the opposite order).