Feature Request: Booking Add-ons

I'd love to see support for optional booking add-ons that clients can select during the booking process.

For example, a hairdresser could offer:

Cut (+45 mins) Blow dry (+30 mins) Treatment (+15 mins)

Or, as a tutor, I could offer:

30-minute session extension (+30 mins) Essay marking add-on Personalised revision pack

Ideally, add-ons would:

Increase the booking price automatically. Add time to the appointment where applicable. Be optional, with clients able to select multiple add-ons. Appear in confirmation emails and calendar events.

This would make Lunacal much more flexible for service-based businesses without requiring separate booking pages for every service combination