Booking confirmation and retries

• A 200 response means the delivery has been booked. Save the returned taskId; do not submit another booking.
• If the requested service is unavailable, Quiver may accept the booking using another available service, preferring Next Day. Use the returned deliveryType and delivery window as the confirmed booking details.
• If you receive “already exists”, use the existing task identified in the error. Do not change merchantOrderId or add suffixes to retry the same booking.
• If a request times out, check for an existing delivery before resubmitting. You can query GET /task/deliveries using the original merchantOrderId.