Send confirm attendance email to every registrant such that:
Email has been verified
Registrant does not appear on the waitlist
Registrant has not been sent an attendance confirmation email yet
Send attendance confirmation email
Send confirm attendance email to an individual:
Note, this action removes the user from the waitlist if they are on it, and sends the attendance confirmation email regardless of whether they've already gotten one.
Send individual attendance confirmation
Send confirmation email to sitting ducks:
Note, this action sends confirmation attendance emails to people who have received them, but have not confirmed/denied their attendance yet.
Send confirmation email to sitting ducks