End seat assignment

End a seat assignment; only valid while the row is still open. For a live row this stops the seat being counted, effective now. For a not-yet-started (scheduled) row it cancels the schedule and re-extends the assignment it superseded, so the prior plan resumes for the months it would have covered.

curl -X POST "https://example.com/seat-assignments/497f6eca-6276-4993-bfeb-53cbbbba6f08/end"

{  "id": null,  "user_id": null,  "provider": "claude",  "plan": "string",  "effective_from": "2019-08-24T14:15:22Z",  "effective_to": "2019-08-24T14:15:22Z"}