Moves the assignment onto the current published version of another template in one accounts transaction, so the account is never seen unassigned. The assignment keeps its id; it takes the new template, version, overrides and materialized_config, and the account's sleeves are updated the same way create does: a sleeve the old template managed that holds a strategy the new template funds is adopted with its holdings, the rest wind down. 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 changes, nothing is saved and the response is 409 sleeve_push_rejected. The template the assignment already follows is 409 same_template; a newer version of it is an update. An organization whose assignments have not moved to accounts yet gets 409 stage_off.