code: func (jb *JSONBuffer) UnmarshalJSON(data []byte) (err error) {
  	var str string
  	err = json.Unmarshal(data, &str)
  	if err != nil {
  		return err
  	}
  	*jb, err = base64URLDecode(str)
  	return
  }
docs: // UnmarshalJSON decodes a JSONBuffer to an object.