Integrate Thanx's loyalty API to look up a guest and apply an eligible reward at checkout, and confirm partner-gated access before committing to the build

Steps

1. Confirm Thanx partner/API access with Thanx directly — like most restaurant loyalty vendors, Thanx does not offer a fully public self-serve developer signup and typically requires a partnership or customer relationship
2. Once credentials are issued, implement guest lookup at the point of sale (commonly by phone number) before tender to check for available rewards or store credit
3. Apply the identified reward or discount to the order total prior to payment capture, following the vendor's specified sequencing so tax/discount calculation stays correct
4. Report the completed transaction back to Thanx after payment so loyalty accrual (points/visits) is recorded against the correct guest
5. Handle the no-match case (guest not found or no reward eligible) as a normal checkout path rather than an error, so staff aren't blocked from completing the sale