The DNSv2 handler now provides a direction label for most metrics. A configuration parameter should be provided to allow filtering of metrics for only specific direction.

This could be accomplished using a filter parameter, such as:

"filter": {
    "only_xact_directions": [ 
      "in",
      "out",
      "unknown"
    ]
  }

Or this could be accomplished using metric groups:

"metric_groups": {
  "enable": [
      "in",
      "out",
      "unknown"
  ]
}

Either way, it should (ideally) be the same as for the Flow handler #577