Rezzy: Wait for cancellation events to attach before processing messages (Airbnb)

Following up in the same vein as the instant booking hotfix that shipped in late July -- I've now seen the same shape of that issue on the cancellation side.

The scenario: guest cancels their reservation through Airbnb and includes a message with the cancellation (a "sorry we can't make it now" note, apologies, etc.). Rezzy processes the message before the cancellation event has fully attached to the booking, so it responds as if the booking were still active -- typically with cancellation instructions ("head into your Airbnb reservation and use the cancellation option there") and unprompted refund commentary ("the refund will be determined by the cancellation policy shown on your booking"). Makes us look uninformed about our own booking status and is confusing for the guest who literally just canceled.

This is what was happening with instant bookings before the hotfix shipped. Would love to see the same wait-for-event-to-attach pattern applied to cancellations.