Allow external Helm templates

[pjgg]

As an end user, I would like to provide my own templates.

At the of the day each company has its own K8s cluster configuration. Some of them have Istio and need deployments with two containers per "deployment", others could have Prometheus and need to add some extra labels to the deployments etc... Currently, I could not find a way to use my own templates based on the generated values.yaml in order to generate my company required k8s.yamls

Note that the values.yaml doesn't have any meaning by themselves, are the templates that give meaning to every values field. So, for example, a developer could set a String in a field that should be an Integer because are the templates that will handle this String and convert it into an Integer based on some custom logic.

For example

Values.yaml

volumePermissions:
      securityContext:
        runAsUser: "auto"

custom template

 {{- if eq ( toString ( .Values.volumePermissions.containerSecurityContext.runAsUser )) "auto" }}
              chown `id -u`:`id -G | cut -d " " -f2` {{ .Values.primary.persistence.mountPath }}

...and at the end are the templates that will set the right value to this field according to the company's needs.

[Sgitario]

I really like this idea +1