[Feature]: Planned incidents/maintanence

[NilsMoller]

What do you imagine 💭

I am changing some hardware in my main home server, which means the services running on it will be down.
This is not an "incident" necessarily, but scheduled maintanence.

It would be great to have this as a possibility. It can be integrated into the existing incident report as a different status.

I have checked the other issues and pull-requests for similar issues.

• [x] I've checked existing issues
• [x] I've checked existing pull-requests

[KSJaay]

Maintenance is already implemented but I just need to add the UI. I'll add that to my list and make sure that's done soon.