Document Metrics Server TLS follow-up

TODO.md

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+# TODO
+
+## Enable Trusted Kubelet Serving Certificates
+
+Context:
+Metrics Server currently uses `--kubelet-insecure-tls` because Talos kubelet
+serving certificates are not trusted by metrics-server by default.
+
+Goal:
+Remove `--kubelet-insecure-tls` from `apps/metrics-server/values.yaml`.
+
+Required work:
+- Enable kubelet server certificate rotation in the Talos machine config:
+
+```yaml
+machine:
+  kubelet:
+    extraArgs:
+      rotate-server-certificates: true
+```
+
+- Add CSR approval for kubelet serving certificates, for example with
+  kubelet-serving-cert-approver.
+- Apply the Talos config and reboot/restart kubelets as needed so new serving
+  certificates are requested.
+- Confirm kubelet serving CSRs are approved and issued.
+- Remove `--kubelet-insecure-tls` from Metrics Server.
+- Verify Metrics Server still scrapes all nodes.
+
+Verification:
+
+```bash
+kubectl get csr
+kubectl -n kube-system logs deploy/metrics-server
+kubectl top nodes
+kubectl top pods -A
+```
+
+Reference:
+- https://docs.siderolabs.com/kubernetes-guides/monitoring-and-observability/deploy-metrics-server