code: public static RequestedAttribute PERSON_IDENTIFIER(Boolean isRequired, boolean includeFriendlyName) {
      return create(AttributeConstants.EIDAS_PERSON_IDENTIFIER_ATTRIBUTE_NAME,
        includeFriendlyName ? AttributeConstants.EIDAS_PERSON_IDENTIFIER_ATTRIBUTE_FRIENDLY_NAME : null,
        Attribute.URI_REFERENCE, isRequired);
    }
docs: Creates a {@code RequestedAttribute} object for the PersonIdentifier attribute.
  
  @param isRequired
  flag to tell whether the attribute is required
  @param includeFriendlyName
  flag that tells whether the friendly name should be included
  @return a {@code RequestedAttribute} object representing the PersonIdentifier attribute