code: function whatError(error) {
    if (error.BadQuery || error.ValidationError) {
      return "Bad Request: Request parameters are malformed.";
    } else
    if (error.ModelExists) {
      return "Conflict: Model already exists with these attributes.";
    } else
    if (error.ModelExists===false) {
      return "Conflict: Model does not exist.";
    } else {
      return "Internal Server Error";
    }
  }
docs: Handle errors