Update Flutter samples

[TahaTesser]

Looks like all the Flutter samples currently have flutter build apk --release

For instance https://github.com/codemagic-ci-cd/codemagic-sample-projects/blob/d1e842b706861b7f067ae5477903e68363a9cb11/Firebase-App-Distribution/codemagic_firebase_app_distribution_yaml-master/codemagic.yaml#L50

Google requires an app bundle for publishing new apps from Aug 2021.

https://android-developers.googleblog.com/2021/06/the-future-of-android-app-bundles-is.html

Also, Flutter docs prefer app bundles too. https://docs.flutter.dev/deployment/android#building-the-app-for-release

Solution

Update all Flutter samples including this

[TahaTesser]

Also "Install Pods" is included in the "Android Workflow". iOS commands should be removed from Android workflows.

https://github.com/codemagic-ci-cd/codemagic-sample-projects/blob/d1e842b706861b7f067ae5477903e68363a9cb11/Firebase-App-Distribution/codemagic_firebase_app_distribution_yaml-master/codemagic.yaml#L45-L47

[TahaTesser]

Just leaving this feedback for anyone updating Flutter samples

• Update SDK constraints and migrate code samples to null-safety.
• Remove trailing a lot of spaces from .yaml files and script files.

• Update codemagic.yaml and build.gradle to match in the same example. For instance: Here If I follow codemgic.yaml file to create environmental variables with some, I would have to update build.gradle to match the same example. These two files should be using the same variable in the same example.

  https://github.com/codemagic-ci-cd/codemagic-sample-projects/blob/271c020bc094e33a127a876d5bee5cd21bf6e66e/flutter/flutter-android-and-ios-yaml-demo-project/codemagic.yaml#L6-L16 https://github.com/codemagic-ci-cd/codemagic-sample-projects/blob/271c020bc094e33a127a876d5bee5cd21bf6e66e/flutter/flutter-android-and-ios-yaml-demo-project/android/app/build.gradle#L52-L61

[K-Codemagic]

Projects are updated.