Add cancellation reason field for notification

appstore/notification.go

@@ -56,6 +56,7 @@ type NotificationReceipt struct {
 	OriginalPurchaseDate
 	NotificationExpiresDate
 	CancellationDate
+	CancellationReason string `json:"cancellation_reason,omitempty"`
 }
 
 type NotificationUnifiedReceipt struct {
@@ -111,4 +112,5 @@ type SubscriptionNotification struct {
 
 	// Posted only if the notification_type is CANCEL.
 	CancellationDate
+	CancellationReason string `json:"cancellation_reason,omitempty"`
 }