Update booking question answers for an appointment

Updates one or more booking question answers on the appointment. The body's custom_questions keys must match the column_name of each booking question (as returned by the GET endpoint). Built-in fields (e.g. guest_phone, event_date, venue_name) are also accepted here.

Only the keys you include are touched — other answers on the appointment are preserved.

Note: booking questions are sourced from the appointment's calendar. Appointments not created from a calendar (e.g. Quick Add) have no associated questions, so this endpoint is a no-op for them — use PATCH /api/v1/appointments/{id} to update guest/venue/event fields directly in that case.

Required permission: assigned_appointment_write or unassigned_appointment_write