anchor.diff:  --------------------------------------------------
   {
     "set": {
  -    "field": "received"
  +    "field": "received",
       "value": "{{_ingest.timestamp}}"
     }
   }
  
positive.code: --------------------------------------------------
  {
    "set": {
      "field": "{{service}}"
      "value": "{{code}}"
    }
  }
  
negative.code: --------------------------------------------------
  {
    "set": {
      "field": "_source.my_field",
      "value": 582.1
    }
  }
  