{ id: Id; }Deletes an assignment candidate for the assignment. It is forbidden to remove a candidate from a finished assignment if the action is called externally.
If the assignment_candidate/user_id is equal to the request user id, the user needs assignment.can_nominate_self, else the user needs assignment.can_nominate_other.
In both cases: If the assignment phase is voting, the request user also needs assignment.can_manage.