Add a notification preview / test screen [1 day]

[pfent]

Follow up from previous issues; #879, #1162, #1165

Even though we really tried to fix this issue, we're still getting occasional crashes in NotificationScheduler. Also the current way of throttling Notifications isn't exactly nice or precise :disappointed:.

As a first step to tackle this, I'd like to introduce a notification preview screen (probably buried somewhere in the settings), which displays all scheduled notifications.

Added benefit:

• Users see all notifications we have currently scheduled for them
• We can give users more control over the notifications, maybe even allow them to adjust the frequency we schedule some notifications
• Add a possibility to debug notifications and enhance the intelligence part of notification scheduling

[kordianbruck]

Good idea, this would also allow for devs an easier access to check if their coded notification actually works...

[thellmund]

Great idea to make debugging easier. I don’t think it will be of interest to end users, but if we bury it “somewhere in the settings”, that should be fine.

[kunzef]

Hey, just wanted to know if the preview is still needed? If so I would like to try to implement it.