json_schema: {
      "$schema": "http://json-schema.org/draft-04/schema#",
      "additionalProperties": false,
      "properties": {
          "customer": {
              "type": "string"
          },
          "message": {
              "type": "string"
          },
          "recipients": {
              "items": {
                  "type": "string"
              },
              "type": "array"
          },
          "sender": {
              "type": "string"
          }
      },
      "required": [
          "customer",
          "message",
          "recipients"
      ],
      "type": "object"
  }