json_schema: {
      "$schema": "http://json-schema.org/draft-04/schema#",
      "type": "object",
      "properties": {
          "version": {
              "oneOf": [
                  {
                      "type": "string",
                      "minLength": 1,
                      "maxLength": 255
                  },
                  {
                      "type": "null"
                  }
              ]
          },
          "slug": {
              "type": "string",
              "minLength": 4,
              "maxLength": 63,
              "pattern": "^[0-9a-z-]*$"
          }
      },
      "additionalProperties": false
  }