[Android] AGP 9 / built-in Kotlin compatibility

[BriceFab]

Summary

Consumers are moving to AGP 9 with android.builtInKotlin=true and android.newDsl=true. This plugin’s Android Gradle config should follow Flutter’s built-in Kotlin path so it does not rely on obsolete KGP application patterns under AGP 9.

Ask

Please track and implement migration per:

https://docs.flutter.dev/release/breaking-changes/migrate-to-built-in-kotlin/for-plugin-authors

Context

• flutter/flutter#184836 — ecosystem → built-in Kotlin
• #101 addressed AGP 8 / namespace, not AGP 9 / built-in Kotlin / new DSL.

Thanks for considering.

[manuel-goester-n41]

👋 Flagging that we're affected by this too: Flutter 3.44 / AGP 8.x warns that in_app_review (latest 2.0.12) still applies the Kotlin Gradle Plugin, and it would block moving our app to AGP 9. For now we're staying on AGP 8.11.1 and tracking this issue rather than working around it.

It looks like #180 already proposes the built-in-Kotlin migration — is there anything that would help move it forward? Happy to test a pre-release build against a real app if that's useful. Thanks for maintaining the plugin! 🙏