Investigate Push Notification Frameworks

Application developers might want to send notifications from a server to users of their applications. The big platform vendors provide native APIs to do that:

Windows Push Notification Services (WNS): https://learn.microsoft.com/en-us/windows/apps/design/shell/tiles-and-notifications/windows-push-notification-services--wns--overview
Android Firebase Cloud Messaging (FCM): https://firebase.google.com/docs/cloud-messaging (also cross plattform)
Apple User Notifications Framework: https://developer.apple.com/documentation/usernotifications

Notifications can be pushed to the end user devices through a REST API on Microsoft/Apple/Google servers.

Scope: We should investigate how these frameworks operate and if we can wrap some boilerplate code behind cross-platform Qt APIs. To do that we can build a prototypical Qt application that receives push notifications (triggered through the Microsoft/Apple/Google servers) and reacts with a custom piece of code. Ideally the front end will be cross platform accessing the platform dependent backend through a unified API.

Testing: Automated testing is not considered useful at this stage, manual tests are sufficient. Triggering the notification might be achieved with QNetworkAccessManager in the test application, the test will be successful if the push notification arrives.