How to identify change in Device token after iOS update without opening app?

We have an App in App Store which is facing a different kind of scenario where users are missing out notifications after iOS updates. 

We have already covered the scenario, Where we are registering app on every launch using .registerForRemoteNotifications() inside didFinishLaunchingWithOptions. And in case of a notification address change, we are forwarding the new notification address to our provider server.

But, We come up with a scenario where the user updates his OS on his iPhone and doesn’t open his app. Also, The device token gets invalidated or expired after the update. So the User stops getting notifications. The only work he can do is to launch the app to register for remote notification and get a new device token after the iOS update. 

So, We would like to know any best practices available or workaround available that can fix our problem until the user open ups the app to get the updated device token after the iOS Update. 

Also, Is there any way from the server side by which our server can communicate with the APNS server and can identify that the APNs token has expired or any other issue is there with this Device token? So that we can let users know to open the app.

As, This is a healthcare app and it is a very critical issue for us to miss out notifications. And due to this issue, a lot of users are getting impacted.

How to identify change in Device token after iOS update without opening app?
 
 
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