Data object passed to Liquid templates
entries: TemplateEntry[]
listing_names: string
attendee: TemplateEntry["attendee"]
ticket_url: string
currency: string
amount_owed: string
Order-level outstanding balance in minor units (as a string, for the
currency filter); "0" when nothing is owed. Positive when a booking was
taken without collecting payment (e.g. no payment provider configured).