Transaction 对象
transactionIdentifierstring - 成功加入队列的事务的唯一标识transactionDatestring - 事务被加入队列的时间originalTransactionIdentifierstring - App Store恢复的事务的标识符transactionStatestring - 事务状态, 可以是purchasing,purchased,failed,restored或deferred.errorCodeInteger - 处理事务时发生错误时的错误代码。errorMessagestring - 处理事务时发生错误时的错误消息。paymentObjectproductIdentifierstring - 购买产品的标识符。quantityInteger - 购买数量。applicationUsernamestring - 系统上不透明的用户帐户标识符。paymentDiscountPaymentDiscount (optional) - The details of the discount offer to apply to the payment.