Add /cc quick command
Sometimes we want someone to be aware of an issue or merge request (issuable), however the only tool we offer for that is to @
mention them. This, however, results in them being subscribed to the issuable until they themselves opt-out, but we only wanted to "ping" them for awareness.
/cc [user]
would create a Notification and ToDo for user
without subscribing them to further updates.