Cancel an order (action variant)

Cancel a submitted order. Functionally equivalent to DELETE /shop/orders/{orderId} but exposed as a POST action so it can sit alongside the other lifecycle transitions (reserve, submit, settle, no-show) under a consistent POST .../{verb} shape.

Each line item is cancelled in turn — bookings (appointments, area bookings, sessions, table reservations) are cancelled and any held resources released; purchases (vouchers, memberships, retail products) are voided; and any package items follow the cancellation rules of their underlying components. Payments remain attached to the order so they can be refunded separately via POST /shop/orders/{orderId}/payments/{paymentId}/refunds or absorbed into a credit note.

Fires the internal BasketCancelled event, which downstream integrations subscribe to for PMS/CRM sync.