test external metric

$ kubectl get --raw "/apis/external.metrics.k8s.io/v1beta1" | jq .
{
  "kind": "APIResourceList",
  "apiVersion": "v1",
  "groupVersion": "external.metrics.k8s.io/v1beta1",
  "resources": [
    {
      "name": "gitlab_runner_jobs_builds_concurrent_saturation",
      "singularName": "",
      "namespaced": true,
      "kind": "ExternalMetricValueList",
      "verbs": [
        "get"
      ]
    }
  ]
}
$ kubectl get --raw "/apis/external.metrics.k8s.io/v1beta1/namespaces/default/gitlab_runner_jobs_builds_concurrent_saturation" | jq .
{
  "kind": "ExternalMetricValueList",
  "apiVersion": "external.metrics.k8s.io/v1beta1",
  "metadata": {},
  "items": [
    {
      "metricName": "gitlab_runner_jobs_builds_concurrent_saturation",
      "metricLabels": {},
      "timestamp": "2022-06-02T15:31:05Z",
      "value": "0"
    }
  ]
}