I’m working on an app and need to implement a feature that sends push notifications if a Firestore document hasn’t been updated for a certain period of time. I’m considering using either OneSignal or Firebase Cloud Messaging (FCM) for this purpose. Here are my requirements:

1. Read data from Firestore.
2. Check if the data has been updated within a specified time frame.
3. If the data hasn’t been updated, send a push notification.

Given these requirements, which service would be more suitable, OneSignal or FCM? Additionally, any guidance or example code on how to implement this would be greatly appreciated.

Thanks in advance for your help!