Use labels suggested by Kubernetes and Helm best practices

[pinkavaj]

Close #496

This improves the compatibility and makes it easier to work with various tools, which take advantage from the assumption of existence of those labels.

• https://helm.sh/docs/chart_best_practices/labels/
• https://kubernetes.io/docs/concepts/overview/working-with-objects/common-labels/

Changing the selectors is breaking change, so the bump of the major version of the helm chart.

I'm not sure about the original intention of the use of reloader.matchLabels, it seems to me they kind of duplicate the reloader.labels, but I would like to keep the amount of changes at minimum.

The chart was tested with the following values:

reloader:
  deployment:
    replicas: 2
    priorityClassName:
  enableHA: true
  logFormat: json
  podDisruptionBudget:
    enabled: true
  podMonitor:
    enabled: true
  readOnlyRootFileSystem: true
  reloadOnCreate: true

[msafwankarim]

Similar change was added in #835 and later reverted to fix the bug #897. This change will potentially reopen the bug #897

[pinkavaj]

Thanks for mentioning the issue, I'm aware of it and I did my best to avoid the same situation happens again, the labels are now set systematically for all resources, which should prevent this at the cost of need to force-reconciliate during the upgrade. (thus the change of the major version of the helm-chart)

[Felix-Stakater]

Hi @pinkavaj!

Thank you for your contribution! I do think that this looks correct and will not trigger the mentioned bug.

However making a major release means more work both for us writing change-logs and for users reading them to validate major upgrades, so I'm hesitant to upgrade the major version on a technicality.

I do also see your point about standard tooling and such so I would like to propose we split this into 2 PRs.

The first will keep almost all changes, except the reloader-match-labels.chart will have the old keys app and release. We move the keys app.kubernetes.io/name and app.kubernetes.io/instance into reloader-labels.chart.
This is a minor release which could be released very fast to solve for your use-case.

The second one would change the keys used in the reloader-match-labels.chart and remove the old labels app and release entirely. This can be merged the next time we make a major release.

PS. You also have a merge conflict which would need to be resolved. :)