Group services by servicegroup

[duncanmmacleod]

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

I would love to be able to group services into cubes by servicegroup.name. I don't think I can do that now (as of 1.3.0).

Describe the solution you'd like

To be able to select servicegroup.name as a dimension in Icinga Cube.

Describe alternatives you've considered

I have half-heartedly considered creating a servicegroup-like custom variable for each service.

Additional context

Service groups as not mapped one-to-one for services (it's many-to-many, in general, I think), so I'm not sure if that breaks the Cube model (which I think is currently one-to-one for the available dimensions). If this is a deal-breaker then I can come up with some sort of 'primary servicegroup'-like custom variable to meet my need.