[in_app_purchase] Replaced deprecated ProrationMode with ReplacementMode

[vongrad]

Replace deprecated ProrationMode in Android's billing client with ReplacementMode.

List which issues are fixed by this PR. You must list at least one issue.
flutter/flutter#128957

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[vongrad]

I had to update the versions in both in_app_purchase and in_app_purchase_android pubspec.yaml files, but now the in_app_purchase cannot resolve the in_app_purchase_android ^0.3.3 dependency when running your pipeline checks. What would be the right approach?

[bparrishMines]

@vongrad It looks like you are changing the name of the ProrationMode class. This is a breaking change for the Android implementation, so it would need a major version bump (e.g. 0.4.0) if that is the goal of the PR.

Also, you are bumping the android implementation in packages/in_app_purchase/in_app_purchase/pubspec.yaml, but that version doesn't exist on pub.dev until this PR would land.

But overall I think we should actually deprecate ProrationMode on the Dart side and add ReplacementMode as a separate enum. And add it as a separate parameter in launchBillingFlow. This would give users time to transition without breaking them immediately.

Since this looks like it is only changing an Android specific method, you shouldn't need to change in_app_purchase in this PR.

[vongrad]

@bparrishMines I agree that its probably better to introduce a new enum for ReplacementMode instead of placing it in as a replacement.
In this case, I suppose I should leave the version of in_app_purchase untouched and only increase the version of in_app_purchase_android. What would you prefer to have as a version number?

[bparrishMines]

Since this is adding a new feature, this should bump in_app_purchase_android to 0.3.3.

[vongrad]

Sure thing, I will submit a new PR during next week once I get some free time.

[vongrad]

I made a new PR with the mentioned changes and in general re-worked it a bit. Please see here: #6515