Replaces the assignment's overrides, recomputes materialized_config from the assigned published version, and updates the account's sleeves the same way create does. The sleeve changes are listed in sleeve_results. Send the revision you last read as expected_revision. If the assignment was saved after that, nothing is written and the response is 409 stale_revision. If accounts refuses the sleeve update, nothing is saved, on the assignment or the account, and the response is 409 sleeve_push_rejected. If accounts gives no clear answer the change is kept, still applying, and the response is 202 with the assignment; reading it by id finishes it, and the revision says whether it was applied. If an earlier change is still being applied, nothing is written and the response is 409 change_in_flight.