A common format which store subsystems use to describe available products.
Includes purchase state via receipt and transactionId.
| metadata | Localized metadata retrieved from the Store. |
| receipt | A purchase receipt, if owned. Otherwise null. |
| storeSpecificId | The store-specific ID. |
| transactionId | The purchase transaction ID, if owned. Otherwise null. |
| type | The ProductType. |
| ProductDescription | Create a ProductDescription. |