Use nextcloud notifications as time alarm

[christianlupus]

As discussed in #1064, it might be useful to provide the possibility to use pain nextcloud notifications as a way to notify the user of an alarm. This might not be the most accurate timing but at least there is a notification.

This issue is there primary to keep track of the general idea.

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Depends on #1067

[MarcelRobitaille]

Is this something that should be configurable in the settings (I am picturing radio buttons for NC notification, browser notification, nothing) or should we always do every kind of notification?

[christianlupus]

I see two ways:

1. A global per-user setting. There are ringing, NC notifications, and browser notifications. The user can enable/disable each of them separately, potentially depending on the amount of time to be measured (NC notifications are relatively rough, so no fit for <20 min).
2. The timers could allow the user to individually select the way of notification to be used. Some way of putting checkboxes or so as an additional menu. I do no know a good way to style it ATM.

[github-actions]

This PR/issue depends on:

• Create an app configuration #1067
  By Dependent Issues (🤖). Happy coding!