Checks that the current user may reassign the request, using the same rule as the reassign endpoint, then lists the
targets of one type. User: active users matching a query of two or more characters, preceded by the current user when
the request is assigned to a queue or role. Queue: the org's queues matching the query (all when it is empty).
Role: non-deleted roles matching a query of two or more characters. The current assignee is never listed.