New sample: in-app purchases, Google Play Billing

[jonathanpeppers]

I think this should be a MAUI sample, we could initially implement for Android. Then iOS/Catalyst next. Last Windows.

The app generally, I think it could be something like:

• Load a list of purchases
  • Show progress indicator
  • Show prices and title, description, etc., price in user's currency
  • Show if any of the purchases are owned (non-consumable, durable)
  • Tap to buy an unowned purchase
• Restore purchases button, will refresh (non-consumable, durable purchase) status

Some links:

• Google docs:
  • https://developer.android.com/google/play/billing
  • https://developer.android.com/google/play/billing/integrate
• A random sample: https://github.com/Catappult/google-play-billing-samples
• Archived MAUI plugin: https://github.com/jamesmontemagno/InAppBillingPlugin

Start with the library that is known to work:

• https://www.nuget.org/packages/Xamarin.Android.Google.BillingClient/7.1.1.4
• Later we can migrate to 8.0.0 and see what issues occur from the upgrade.
• Next. we can add iOS & Catalyst support.
• Next, we can consider Windows.