Feature: Exposing K8s labels from tls secret

[fedorenkobn]

Summary

It would be highly beneficial if the x509-certificate-exporter could support exposing labels as metrics from TLS secrets. This feature would allow users to filter and select specific TLS secrets by their labels in Grafana.

[KongrooParadox]

This feature would be beneficial to a usecase I have encountered with my current employer.

We use certmanager to handle some of our certificates and for reasons some certificates are renewed manually.

It would be helpful to be able to export a list of labels via the secretExporter for example.

This would enable us to set custom alerting rules with a larger window for certs with the "manual" label, and only emit an alert when a "certmanager" cert has passed it's automated renewalDate.