pikvm: Add user for Prometheus metrics

PiKVM exports metrics in Prometheus format, but requires authentication
to scrape them.

group_vars/pikvm.yml

@@ -7,3 +7,14 @@ pikvm_users:
 - username: dustin
   password: >-
     {{ lookup('pipe','rbw get --folder Pyrocufflink ' + ansible_hostname + ' dustin') }}
+- username: prometheus
+  password: >-
+    {{
+      lookup(
+        "kubernetes.core.k8s",
+        kind="Secret",
+        namespace="victoria-metrics",
+        resource_name="vmagent",
+      ).data["pikvm.password"]
+      | b64decode
+    }}