code: private void addPreflightOptionsRequestSupport(RestExpress server, CorsOptionsController corsOptionsController)
      {
  	    RouteBuilder rb;
  
  	    for (String pattern : methodsByPattern.keySet())
  	    {
  	    	rb = server.uri(pattern, corsOptionsController)
  		    	.action("options", HttpMethod.OPTIONS)
  		    	.noSerialization()
  		    	// Disable both authentication and authorization which are usually use header such as X-Authorization.
  		    	// When browser does CORS preflight with OPTIONS request, such headers are not included.
  		    	.flag(Flags.Auth.PUBLIC_ROUTE)
  		    	.flag(Flags.Auth.NO_AUTHORIZATION);
  
  	    	for (String flag : flags)
  	    	{
  	    		rb.flag(flag);
  	    	}
  
  	    	for (Entry<String, Object> entry : parameters.entrySet())
  	    	{
  	    		rb.parameter(entry.getKey(), entry.getValue());
  	    	}
  
  	    	routeBuilders.add(rb);
  	    }
      }
docs: Add an 'OPTIONS' method supported on all routes for the pre-flight CORS request.
  
  @param server a RestExpress server instance.