feat: allow custom serviceMonitor labels

[RedSunEmpire]

Hello,

There are cases where Prometheus watches which serviceMonitors to scrape based on custom labels, it will be useful to have that option in the helm-chart.

This is how the 'serviceMonitor' would look like with custom labels defined in values.yaml:

serviceMonitor:
  enabled: false
  interval: 60s
  scrapeTimeout: 20s
  labels:
    prom-scrape: true

[till]

Is an empty value in yaml also false? Could you add an empty default in the values file as well?

[RedSunEmpire]

Yes, an empty value in values.yaml is considered 'false' and no custom labels will be added if it is not defined.

I have added a default empty 'labels' key to the serviceMonitor resource in values.yaml, let me know if anything else needs to be changed.

[till]

@RedSunEmpire Thank you, will try to roll a release this week to update the helm chart.

[RedSunEmpire]

Thank you as well for the quick responses and merge.

[till]

@RedSunEmpire I've updated the chart. Had to manually push it. And for some reason, I made 0.2.3, instead of 0.2.0.