Android Example Google Play Billing v.7 Subscription Example

This is a modified example, based in the original example from @Erel.
The previous example only make purchases.
This new example utilizes the Google Play Billing library v.7, changes the purchase to subscription and remove the ads.

Due the requirements of the new library version, you need to access the Play Console, create a new app (if it don't exists) and:
1 - Get the License Key
2 - Create the subscription products