Appointments+ Notifications: After Appointment Completed

This is a add-on feature that is greatly needed. I have seen multiple threads on this and the one linked below spells out all the code necessary. Please build this into Appointments+ so we don't have to hack your plugin to make it work.

https://premium.wpmudev.org/forums/topic/appointments-hookaction-for-completed-appointment?replies=5#post-808155