If a timeout occurs on the PayPay side, is the cancellation process executed by PayPay? If so, what should the merchant system do?
If the total amount of unitprice of orderItems in multiple items exceeds the amount set in amount, will an error occur in the system? If there is no error, is the amount actually traded the amount in the amount item? If 0 is not allowed in the unit price
Can It use the same merchantPaymentId multiple times?