Allow merchant to set a minimum amount of bookings for an experience to happen

In some cases, merchants want to specify a minimum number of bookings for a time slot. If that amount isn't met by a specific time before the start time, the merchant will be notified and can cancel, transfer, or restock those experiences.

More details:

• Regardless of how many variants (e.g. Standard, VIP, etc), and...

• irrespective of how many individual/unrelated parties book together or separately...

• the merchant wants a minimum to conduct the experience even if it comes from separate sales.

e.g. "I don't want to staff up that time slot unless there are at least two bookings, even if from separate orders."