Webhook options for various Service Statuses#883

Add Service related webhooks so that updates can be sent out for items such as;

Service ID
Service Status - will the service run (has it met group booking minimums?)
Service Updates - has any new bookings be created
Group Booking Participants - how many bookings for a particuar time Group Booking Minimum
Group Booking Maximum
Service duration
Service start time (or Time till service starts)

Maybe possibly add a way for us to create custom webhooks using predefined codes, in a similar way to how it is setup to name Zoom meetings.