Disable monitoring for vendor sites

[Daniel-WWU-IT]

Add the ability to disable monitoring for vendor sites in the accounts panel; less restrictive than authorization status, so sites appear in the main list but aren't included in Prometheus/Grafana.

[Daniel-WWU-IT]

Currently, if a service has is_monitored set to true, it will be included in Metrics gathering (and will thus appear on the Dashboards). For health checks, it has to be of type sciencemesh, type community is not exported through the PromSD exporter.

We need a way to disable monitoring for a site without unauthorizing it (as that would remove it from the main sites list as well). It also needs to be considered whether/how to include them in the /cs3 endpoint.