code: func (e *Errors) Add(fieldNames []string, kind, message string) {
  	*e = append(*e, NewError(fieldNames, kind, message))
  }
docs: // Add adds an Error associated with the fields indicated by fieldNames, with
  // the given kind and message.
  //
  // Use a fieldNames value of length 0 to indicate that the error is about the
  // request as a whole, and not necessarily any of the fields.
  //
  // kind should be a string that can be used like an error code to process or
  // categorize the error being added.
  //
  // message should be human-readable and detailed enough to pinpoint and resolve
  // the problem, but it should be brief. For example, a payload of 100 objects
  // in a JSON array might have an error in the 41st object. The message should
  // help the end user find and fix the error with their request.