Integrate Google In-App Billing in Android App

I'm looking for an experienced Android developer to integrate Google In-App Billing into my existing app. This app, which is developed in Kotlin with clean architecture is designed to sell a monthly subscription and one purchasable product.

Key Requirements:
- Expertise in Kotlin and Android development
- Proven track record of integrating Google In-App Billing
- Experience with developing services-based in-app purchases

The successful candidate will help enhance the app's monetization potential through efficient and seamless integration of the billing system.