sending data.
      */
      withCredentials: {
        type: Boolean,
        value: false
      },

      /**
       * Content type to use when sending data. If the `contentType` property
       * is set and a `Content-Type` header is specified in the `headers`
       * property, the `headers` property value will take precedence.
       * If Content-Type is set to a value listed below, then
       * the `body` (typically used with POST requests) will be encoded accordingly.
       *
       *    * `content