awaitPromotionalOfferResult
suspend fun <Error class: unknown class>.awaitPromotionalOfferResult(discount: <Error class: unknown class>, storeProduct: <Error class: unknown class>): Result<<Error class: unknown class>>
App Store only. Use this method to fetch a PromotionalOffer to use with awaitPurchase.
Return
A Result containing a PromotionalOffer if successful, and PurchasesException in case of a failure.