Unified Confirmation Emails

When a booking a volunteer or group for 5 or more volunteering slots, it becomes overwhelming to send out a confirmation email for each registration.

Similar to when a volunteer books themselves for multiple slots and gets one confirmation email, it would be nice to have this ability from the admin side.

I know it will be more complicated to enable across multiple events, but maybe this could be a staged release with limited functionality initially (limited to single events) and then find a way to enable it for as many events as you want.