How to add contact to booking?

How can I add a contact to a booking, or create a booking with more than one contact?

When creating a booking via API, it seems one is limited to creating a single contact. There doesn't appear to be a way that I have found to add another contact to the booking via API.

It doesn't matter to me if it is in one step or three, (Create booking, create 2nd contact, add 2nd contact to booking). It would be really nice to be able to automate this.

At this point I have to create a duplicate booking and rely on a staff member to merge the two bookings together to get both contacts on the booking.

https://developers.eventtemple.com/reference/createfullbooking implies it is possible, but doesn't document it.

"Bookings can be created with contacts, events and line items. ... To associate a booking with a contact, read more here."

Unfortunately here takes one to https://developers.eventtemple.com/reference/createbooking which has nothing to do with associating a contact with a booking. The examples on the first page don't even show including a contact. Maybe I can try sending a list of contacts...