I was wondering how mobile news apps send messages where if you click on the push notification, the app takes you to the specific article. I am trying to perform a similar task but have the user generate a message and send it to another user. When the user on the other end receives the message, they should be taken to another view that displays the message data.
Would I use the Firebase In-App Messaging or would I need an external server with the Firebase Admin SDK implemented?
You need to make use of userNotificationCenter(_:didReceive:withCompletionHandler:)
, firing the appropriate logic based on the contents of your notifications, or the action selected by the user.
See this blog post for an overview of how you can open a specific view controller from the background. As an example, this project on GitHub uses Firebase and seems to do what you're trying to do.