Allows Cloudbeds to acknowledge a booking on your OTA from the Cloudbeds side.

IMPORTANT: Please contact us to enable this capability for your channel. It
is NOT enabled by default.

One AckBooking is sent per booking, after the booking has been imported and
handed to the property's PMS. Bookings are not acknowledged in the order they
were delivered — cancellations are processed ahead of new and modified
bookings — so do not infer any ordering from the sequence of calls. Use
acknowledgement_id or version to identify which delivery is being
acknowledged:

• For bookings you pushed to us with the BookingCreate callback, we return
  acknowledgement_id, one of the acknowledgement_ids we returned in that
  callback's response.
• For bookings we pulled with GetBookingList, we return version, the value
  you supplied for that booking in the GetBookingList response.

A booking that is delivered again — a modification, or a redelivery after a
failed import — is acknowledged again, with the identifier belonging to that
delivery.

If the booking cannot be acknowledged the error code should be provided. Here
are possible error codes:

• 4004 - booking cannot be acknowledged. The reason is provided in the msg field.