[kubeletstatsreceiver] Allow user to define a custom caCertPath

[dloucasfx]

Component(s)

No response

Describe the issue you're reporting

Unlike common k8s deployments, the AKS deployment does not generate kubelet’s self-signed certificate from the CA that issues the kube-apiserver certificate, so the Service Account CA /var/run/secrets/kubernetes.io/serviceaccount/ca.crt which is added to the receiver’s client rootCA will still fail to verify the kubelet’s cert.

To address this issue, we need to use a kubelet client with the correct CA that AKS used to generate the cert /etc/kubernetes/certs/kubeletserver.crt

At first I thought that the configtls options ca_file , which is exposed to the receiver, would do the trick, but after going through the code, I have noticed this option is not used when the auth type is serviceaccount.

We should check if ca_file is set and use it instead of the default /var/run/secrets/kubernetes.io/serviceaccount/ca.crt for service account

[github-actions]

Pinging code owners for receiver/kubeletstatsreceiver: @dmitryax @TylerHelmuth @ChrsMark. See Adding Labels via Comments if you do not have permissions to add labels yourself. For example, comment '/label priority:p2 -needs-triaged' to set the priority and remove the needs-triaged label.