As a flight scheduler, I want to add someone to a waitlist for a specific time, so that if the first person cancels, they can automatically replace them on the schedule. The waitlist person would optionally be notified.

I'd rather you just let me know when an appointment is cancelled, so I have the option of booking in the newly available slot, instead of booking a standby reservation like it works now. I should be able to click on an appointment and "subscribe" to it. Maybe I can choose when I'm notified - like for cancellation only, or when any changes are made.