Flutter iap subscription config

* The In-app product id should format: <package_id>_<type>_<number>. Ex: com.app.habitapp_yearly_000 (desc: Annual Subscription, Subscription Display Name: One year subscription, Description: Аll features of the app are available to you)

* The In-app product just works on real device

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Mobile site

# in app purchase
flutter_inapp_purchase:
git:
url: https://github.com/nhancv/flutter_inapp_purchase.git
in_app_purchase: ^0.3.4+16…