Gdx pay android google billing 5 (#249)

* Upgrade to Google Billing 5 (subscriptions and in-app purchases)

Co-authored-by: Lucas Signorini

gdx-pay-android-googlebilling/README.md

@@ -1,6 +1,8 @@
 # InApp purchasing implementation for Google Play Billing
 
-Handles purchases and restores for non-consumable and consumable products, subscriptions support is work in progress and PRs are welcome.
+Handles purchases and restores for non-consumable and consumable products.
+
+Subscriptions are supported with some limitations: the first `SubscriptionOfferDetails` in the list of offers in `ProductDetails` is used.
 
 ## Usage
 
@@ -22,8 +24,13 @@ Add this to your `AndroidLauncher`'s `onCreate` method:
 
     game.purchaseManager = new PurchaseManagerGoogleBilling(this);
 
+## Purchase items
+
+Google Billing allows multiple products in the same purchase. You can change this setting at Play Console - In App Products - Product Setting - Allow Users to purchase multiple products in one purchase. This library forces handling only one product per transaction, so keep this setting "FALSE", or change as you need.
+
+
 ## Testing
 * Upload your compile build with this lib included as an closed alpha build first. This is needed to even being able to add IAPs in the console.
 * Add your IAPs and mark them as active
-* Add testers to your closed alpha build so they see the new IAPs and also add these testers as "licensed testers" (Settings -> Account details -> Licsensed) so they are not being charged
+* Add testers to your closed alpha build so they see the new IAPs and also add these testers as "licensed testers" (Settings -> Account details -> Licensed) so they are not being charged
 * Testers must join the alpha test channel and can test (in my experiences they can also test with a debug build)

gdx-pay-android-googlebilling/build.gradle

@@ -37,7 +37,7 @@ configurations {
 
 dependencies {
     api project(':gdx-pay-client')
-    api 'com.android.billingclient:billing:3.0.1'
+    api 'com.android.billingclient:billing:5.0.0'
 
     testImplementation libraries.junit
 }