| products | The additional products to fetch or existing products to refresh. |
| successCallback | Callback invoked when products are retrieved successfully. |
| failCallback | Callback invoked when the fetch fails for unrecoverable reasons. |
This method may be used to fetch additional products for purchasing, or to refresh metadata on existing products.
Fetched products are added to the existing set of products Unity IAP fetched upon initialization. If the device is offline the request will be retried in the background until online, in the same way as happens during initialization.