Add inventory metrics: helm release version

[gberche-orange]

Describe the bug

As a developer, in order to watch version bumps propagate on systems, I need fluxcd to provide helm related inventory in prometheus metrics.

This is similar to #3106

Steps to reproduce

Currently the gotk_reconcile_condition provides the HelmRelease name, but not its version.

Workaround is to install a distinct exporter such as https://github.com/sstarcher/helm-exporter with the following drawbacks

• from a UX point of view, this provides duplicated/inconsistent metrics
• from a performance perspective, this additional exporter adds loads on the cluster whereas flux helm controller has the data available
• from a security perspective, this implies giving permissions to an additional exporter to inspect helm releases, whereas flux already has the permissions

Expected behavior

Similar to kube_pod_container_info exposed by K8S that includes the image as label, the helm chart version is needed for each flux HelmRelease CR

More details about the kube_pod_container_info below:
see https://github.com/kubernetes/kube-state-metrics/blob/master/docs/pod-metrics.md

container=
pod=
namespace=
image=
image_id=
image_spec=
container_id=
uid=

kube_pod_container_info{container="alertmanager", container_id="containerd://37d82c840c7148233120bb250a059ceec13e86ec586ab5ef51402df8e6f15794", image="quay.io/prometheus/alertmanager:v0.24.0", image_id="quay.io/prometheus/alertmanager@sha256:088464f949de8065b9da7dfce7302a633d700e9d598e2bebc03310712f083b31", image_spec="quay.io/prometheus/alertmanager:v0.24.0", instance="10.42.7.20:8080", pod="alertmanager-alertmanager-2", service="kube-prometheus-stack-kube-state-metrics", uid="c731ad41-af52-46d9-b156-931f80524151"}

Screenshots and recordings

No response

OS / Distro

n/A

Flux version

n/a

Flux check

n/A

Git provider

No response

Container Registry provider

No response

Additional context

No response

Code of Conduct

• I agree to follow this project's Code of Conduct

[mtparet]

Needed here too, so we can plug it into our current system. Weavegitops is great to understand and dig into details but we need to have an overview in a monitoring system to be able managing it.

[stefanprodan]

You can extend the Flux metrics and add the chart version, example here: https://fluxcd.io/flux/monitoring/custom-metrics/#adding-custom-metrics