Checks whether a user's subscription purchase is valid and returns its expiry time.
||The package name of the application for which this subscription was purchased (for example, 'com.some.thing').|
||The purchased subscription ID (for example, 'monthly001').|
||The token provided to the user's device when the subscription was purchased.|
This request requires authorization with the following scope:
For more information, see the authentication and authorization page.
Do not supply a request body with this method.
If successful, this method returns a Purchases.subscriptions resource in the response body.