Webhook to parking bookings events

It is now possible to subscribe to new events related to parking place booking. Added webhook to the "Parking place: Booking cancelled" event - notifications are sent for any cancellation of a booking, regardless of who deleted it and which way. The format of the message is similar to the notification about creating a booking, but specifying the fact of cancellation.
Also added webhook to the "Parking place: Booking confirmed" event. Now notifications are sent for any type of booking confirmation: auto-check-in, remote confirmation or local check-in only.