StoreKit macOS 10.13.2 Beta 2 to GM API Differences

SKProduct.h

Added SKProductPeriodUnit

Added SKProductPeriodUnitDay

Added SKProductPeriodUnitWeek

Added SKProductPeriodUnitMonth

Added SKProductPeriodUnitYear

Added SKProductSubscriptionPeriod

Added SKProductSubscriptionPeriod.numberOfUnits

Added SKProductSubscriptionPeriod.unit

Added SKProduct.subscriptionPeriod

Added SKProduct.introductoryPrice

SKProductDiscount.h

Added SKProductDiscountPaymentMode

Added SKProductDiscountPaymentModePayAsYouGo

Added SKProductDiscountPaymentModePayUpFront

Added SKProductDiscountPaymentModeFreeTrial

Added SKProductDiscount

Added SKProductDiscount.price

Added SKProductDiscount.priceLocale

Added SKProductDiscount.subscriptionPeriod

Added SKProductDiscount.numberOfPeriods

Added SKProductDiscount.paymentMode