* experimental MVP PurchaseManager using Apple StoreKit2 API (#273)

* * experimental MVP PurchaseManager using Apple StoreKit2 API
uses `io.github.dkimitsa.robovm:robopods-storekit-swift` bindings for Swift based StoreKit2 API.
implementation should be considered as POC and might some things might be broken.At least gdx-pay sample app was working with this manager.

* * isEligibleForIntroOffer is checked before filling FreeTrialPeriod as suggested by keesvandieren

* * implemented missing observer callbacks in purchase and restore transactions

* * updated dependency to StoreKit2 bindings with MobiVm release version.

* Update gdx-pay-iosrobovm-apple/src/main/java/com/badlogic/gdx/pay/ios/apple/PurchaseManageriOSApple2.java

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* Update gdx-pay-iosrobovm-apple/src/main/java/com/badlogic/gdx/pay/ios/apple/PurchaseManageriOSApple2.java

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

---------

Co-authored-by: Kees van Dieren <keesvandieren@squins.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: 3 people

build.gradle

@@ -34,6 +34,7 @@ ext {
             mockito_core                            : 'org.mockito:mockito-core:2.7.21',
             robovm_rt                               : "com.mobidevelop.robovm:robovm-rt:$roboVMVersion",
             robovm_cocoatouch                       : "com.mobidevelop.robovm:robovm-cocoatouch:$roboVMVersion",
+            robovm_storekit2                        : "com.mobidevelop.robovm:robopods-swift-storekit2:18.2.0.1",
             support_v4                              : "com.android.support:support-v4:25.0.0"
     ]
 

gdx-pay-iosrobovm-apple/build.gradle

@@ -10,4 +10,5 @@ dependencies {
     api project(':gdx-pay-client')
     api libraries.robovm_rt
     api libraries.robovm_cocoatouch
+    api libraries.robovm_storekit2
 }