API endpoints for maintenance

[indy-independence]

Is your feature request related to a problem? Please describe.

We want to be able to schedule maintenance / downtime of devices via API, for example when triggering an OS/firmware upgrade from NMS we want to suppress alerts for a short while

Describe the solution you'd like

Addition of new API endpoints to add maintenance tasks , probably also list and delete maintenance tasks but not sure we will use those to start Our intended solution is just before the reboot switch command is sent, we make an API call to NAV to start a ~15 min maintenance task. If the API can handle adding up to ~50 tiny maintenance windows with one device each in rapid succession that would be good, or maybe we can also try to schedule a bit longer window for up to 50 devices at a time with one API call

Describe alternatives you've considered

Additional context

We have discussed this in meetings a while back but I think I never actually created the issue on github before (or if I did I can't find it anymore)