Get stats and counters for the subchannel

Example response

{
  "stats": {
    "counters": {
      "total_artifact_count": 10,
      "package_count": 10,
      "project_count": 10,
      "notebook_count": 10,
      "environment_count": 10,
      "mirror_count": 10,
      "group_count": 10,
      "subchannel_count": 10,
      "download_count": 10
    }
  }
}