Payment Integration for Android Flutter App

I need an experienced Flutter developer to integrate a payment gateway such as Stripe into my Android application for recurring payments for the premium version of my app. The app is currently functioning but not live yet and needs this payment gateway integration to be ready for the Google Play store.

Key Requirements:
- Proficient in Flutter development
- Extensive experience with Stripe/Google Pay/Google Play Billing integration
- Previous work with implementing recurring payment systems
- Understanding of e-commerce app requirements
- Ability to deliver high-quality, bug-free code

Please note that the user authentication method has not been decided yet. Your experience and suggestions in implementing secure and user-friendly authentication methods will be highly appreciated.