Improvement - add working example

[bar-tech-dev]

Hello, I very appreciate your plugin! Howewer it could be very nice to see an working example, especially with server side validation for Android.

There is also to things I'm not sure how to implement.

1. How should server response look for Android server validation?
2. How to handle if user renew subscription outside of app? I mean In App Store->Subscriptions, while App is still open? How would app knows that subscription is renewed without event listener?

Best regards,
Bartek