I have a Flutter customer app and a Flutter admin app. I use firebase firestore to store my data and also use firebase authentication. I want to send a FCM push notification from my customer app to the admin app when the customer buys a product from the app.

I tried searching everywhere, but could not find a tutorial on how to send a push notification from a flutter app. The FirebaseMessaging.instance.sendMessage() method is also deprecated. I have read in some tutorials that I can have a cloud function to send the push notification when a document is added to firestore.

As I have no idea on cloud funtions, could anyone point me to some tutorials on how I can achieve the task?