json_schema: {
      "$schema": "http://json-schema.org/draft-04/schema#",
      "type": "object",
      "properties": {
          "id": {
              "type": "string",
              "description": "The message id"
          },
          "content": {
              "type": "string",
              "description": "The message content"
          },
          "meta": {
              "type": [
                  "object"
              ],
              "properties": {
                  "creator": {},
                  "created": {
                      "type": [
                          "string"
                      ],
                      "description": "The subject creation date"
                  },
                  "updated": {
                      "type": [
                          "string"
                      ],
                      "description": "The subject update date"
                  }
              }
          }
      }
  }