Any mentor can claim any mentee using Special:ClaimMentee. When the action is done, is it logged and the mentee receives a notification saying that they have a new mentor.
As a mentor, I have no way to know that a mentee has been claimed from me.
As a mentee, I can be claimed by a mentor without giving my approval.
As a consequence,
- a mentee should have a way to acknowledge that their mentor will change, and if they disapprove, they should be given an alternative (for instance, accessing a special page to ask for another mentor - T292068)
- a mentor should confirm that they are okay to see their mentee being assigned to another mentor. This doesn't apply to a mentor not on the mentors list anymore, or if the mentee made the request.

