Support nested builder in DSL for reactive apps

Fixes: gh-7107

samples/boot/hellowebflux-method/src/main/java/sample/SecurityConfig.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2019 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -25,6 +25,8 @@ import org.springframework.security.core.userdetails.User;
 import org.springframework.security.core.userdetails.UserDetails;
 import org.springframework.security.web.server.SecurityWebFilterChain;
 
+import static org.springframework.security.config.Customizer.withDefaults;
+
 /**
  * @author Rob Winch
  * @since 5.0
@@ -38,10 +40,11 @@ public class SecurityConfig {
 		return http
 			// Demonstrate that method security works
 			// Best practice to use both for defense in depth
-			.authorizeExchange()
-				.anyExchange().permitAll()
-				.and()
-			.httpBasic().and()
+			.authorizeExchange(exchanges ->
+				exchanges
+					.anyExchange().permitAll()
+			)
+			.httpBasic(withDefaults())
 			.build();
 	}