StoreKit iOS 12.4 to 13.0 API Differences

SKArcadeService.h
Added SKArcadeService
Added +[SKArcadeService registerArcadeAppWithRandomFromLib:randomFromLibLength:resultHandler:]
Added +[SKArcadeService arcadeSubscriptionStatusWithNonce:resultHandler:]
Added +[SKArcadeService repairArcadeApp]
SKDownload.h
Added SKDownload.expectedContentLength
Modified SKDownload.contentLength
AvailabilityReplacement
FromAvailablenone
ToDeprecated-[SKDownload expectedContentLength]

SKPaymentQueue.h
Added SKPaymentQueue.delegate
Added SKPaymentQueue.storefront
Added SKPaymentQueueDelegate
Added -[SKPaymentQueueDelegate paymentQueue:shouldContinueTransaction:inStorefront:]
Added -[SKPaymentTransactionObserver paymentQueueDidChangeStorefront:]
SKProduct.h
Removed SKProduct.downloadable
Added SKProduct.isDownloadable
Added SKProduct.contentVersion
SKStorefront.h
Added SKStorefront
Added SKStorefront.countryCode
Added SKStorefront.identifier