message: Support custom metadata when copy to Blob or ADLS Gen2
diff: "copyBehavior": {
  "description": "The type of copy behavior for copy sink.",
  "type": "object"
  + },
  + "metadata": {
  + "type": "array",
  + "description": "Specify the custom metadata to be added to sink data. Type: array of objects (or Expression with resultType array of objects).",
  + "items": {
  + "$ref": "#/definitions/MetadataItem"
  + }
  }
  }
  },
  "copyBehavior": {
  "description": "The type of copy behavior for copy sink.",
  "type": "object"
  + },
  + "metadata": {
  + "type": "array",
  + "description": "Specify the custom metadata to be added to sink data. Type: array of objects (or Expression with resultType array of objects).",
  + "items": {
  + "$ref": "#/definitions/MetadataItem"
  + }
  }
  }
  },
  "name": "NetezzaPartitionOption",
  "modelAsString": true
  }
  + },
  + "MetadataItem": {
  + "description": "Specify the name and value of custom metadata item.",
  + "type": "object",
  + "properties": {
  + "name": {
  + "type": "object",
  + "description": "Metadata item key name. Type: string (or Expression with resultType string)."
  + },
  + "value": {
  + "type": "object",
  + "description": "Metadata item value. Type: string (or Expression with resultType string)."
  + }
  + }
  }
  }
  }
  