Support Android Gradle Plugin 8+

[davidmartos96]

• I have updated Purchases SDK to the latest version
• I have read the Contribution Guidelines
• I have searched the Community
• I have read docs.revenuecat.com
• I have searched for existing Github issues

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There are a lot of things that can contribute to things not working. Having a very basic understanding of your environment will help us understand your issue faster!

Environment

• Output of flutter doctor
• Version of purchases-flutter
• Testing device version e.g.: iOS 15.5, Android API 30, etc.
  Any Android using Android Gradle Plugin 8+
• How often the issue occurs- every one of your customers is impacted? Only in dev?
• Debug logs that reproduce the issue
• Steps to reproduce, with a description of expected vs. actual behavior
  Other information (e.g. stacktraces, related issues, suggestions how to fix, links for us to have context, eg. stackoverflow, etc.)

Describe the bug

Currently the plugin doesn't build when Gradle 8+ is used. That is because the property namespace is mandatory.

Additional context

Other native plugins have been doing this migration recently like the official Flutter plugins camera, shared_preferences...

PR with a fix: #683

[RCGitBot]

👀 SDKONCALL-281 We've just linked this issue to our internal tracker and notified the team. Thank you for reporting, we're checking this out!

[vegaro]

Thanks for opening. We'll look into the PR.

For reference, this is the PR that fixed the official packages flutter/packages#3836

[davidmartos96]

That PR is related and optional. It depends on what minimum requirements you want for the plugin.
The namespace property didn't exist in AGP versions prior to 4.2, so simply adding the property will fail the build for those people.
In any case, the latest Android Studio stable only works with AGP 7.x so if you want to encourage people to have their project up to date you can remove the conditional.
If you want to be more compatible I'd leave the conditional.
https://pub.dev/packages/device_info_plus/changelog

For example, the plus_plugins community plugins have decided to not add the conditional.

[davidmartos96]

There is another previous PR that adds the namespace property. The one you linked adds the conditional.