code: @Nullable
  	static String extractName(@Nullable Object authentication) {
  
  		if (authentication == null) {
  			return null;
  		}
  
  		Expression expression = PARSER.parseExpression(NAME_EXPRESSION);
  
  		return expression.getValue(authentication, String.class);
  	}
docs: Extracts principal name from authentication.
  
  @param authentication Authentication object
  @return principal name