🌱 hack/observability: add capi_machine_status_certificatesexpirydate metric

[chrischdi]

What this PR does / why we need it:

Adds a gauge metric to our kube-state-metrics configuration for exposing a machines .status.certificatesExpiryDate.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #9019

[sbueringer]

the help text sounds a bit wrong

[sbueringer]

Let me know if I should take another look / it works :D

[chrischdi]

Jep, should work now:

# HELP capi_machine_status_certificatesexpirydate Information about certificate exporation date of a control plane node.
# TYPE capi_machine_status_certificatesexpirydate gauge
capi_machine_status_certificatesexpirydate{cluster_name="development-4779",customresource_group="cluster.x-k8s.io",customresource_kind="Machine",customresource_version="v1beta1",name="development-4779-65zw4-pw7qp",namespace="default",uid="3a3065d9-30fd-4b04-ad21-9c76cf1b8932"} 1.722674676e+09

[sbueringer]

Thx! one nit

[sbueringer]

Thx!

/lgtm
/approve

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: be07ed50dfef1f75fe441fad00e6da8fa21206c0

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: sbueringer

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[g-gaston]

/area metrics