Add resource labels to metrics: special characters

[rfrebyLF]

Hello,

We have a quick question about adding resources' labels to metrics in prometheus. Our label use the following syntax:

app.kubernetes.io/components
helm.sh/chart

We have added them inside the value reportResourceLabels, but this return the following error:

{"level":"info","ts":1667552281.1283395,"msg":"Wait completed, proceeding to shutdown the manager"} 
unable to run trivy operator: starting controllers manager: descriptor Desc{fqName: "trivy_image_vulnerabilities", help: "Number of container image vulnerabilities", constLabels: {}, variableLabels: [namespace name image_registry image_repository image_tag image_digest severity k8s_label_app.kubernetes.io]} is invalid: "k8s_label_app.kubernetes.io" is not a valid label name for metric "trivy_image_vulnerabilities"

Prometheus doesn't accept special chars inside metrics labels. Do you have any idea of how we could process our label ?

Thank you for your work with Trivy and your help !

[chen-keinan]

Fixed by #649