A string used to uniquely identify a discount offer for a product.
A string that identifies the key used to generate the signature.
A universally unique ID (UUID) value that you define.
A string representing the properties of a specific promotional offer, cryptographically signed.
The date and time of the signature's creation in milliseconds, formatted in Unix epoch time.
The signed discount applied to a payment
See
https://developer.apple.com/documentation/storekit/skpaymentdiscount?language=objc