Booking Rules - Send test message

[danbuntu]

Is your feature request related to a problem? Please describe.
The ability to send a test message from a booking rules would be very helpful.

So for example if I set a an email to be sent 7 days before the booking I would like to be able to click a button to trigger it so that I can check it's goes to the right people, that rules set against it are correct and that the formatting is correct. Without that I need to wait 7 days to check it.