Make it possible to consume pending notifications when opening the app manually

### Problem description

When notifications get received while the app has been in the background or killed and it gets opened *not* through tapping on one of those notifications (e.g. clicking on the app icon or selecting it in the multitasking screen), there is currently no way to consume these notifications. They can only be consumed when the app gets opened through tapping on a notification.

### Expected behavior

A mechanism should be provided which enables optionally reading the data of those pending notifications and removing them from the system UI when the app gets opened.