Guide: Right way to override variables

[RaSerge]

Hello, CozyDevs!
It's so stupid, but we override cozystack package values straigh in packages/.../.../values.yaml and apply them in build stage with git diff <-> git patch

Please add to documentation (maybe in guides or development part) true way: just put your values in cozystack configmap!

Troubleshooting/debug: render everything by make show from packages/core/platform, find

# Source: cozy-platform/templates/helmreleases.yaml
apiVersion: helm.toolkit.fluxcd.io/v2
kind: HelmRelease
metadata:
  name: <your-package-name>

in the output and check resulting values.

Against a live cluster, you can render single package chart by running make show from packages/system/