Add "Sign in with Apple" to iOS app

I have an educational iOS app that currently supports Google login. I'm seeking a developer to integrate the "Sign in with Apple" feature. This app contains paid content, hence it's essential that subscription status is synchronized across devices.

Key Requirements:
- Implement "Sign in with Apple" feature
- Ensure subscription status is synchronized across devices
- Allow users to link their Apple ID to an existing account

Ideal Candidate:
- Proven experience with iOS app development
- Familiarity with integrating "Sign in with Apple"
- Skills in synchronizing user data across devices
- Experience with implementing account linking functionalities