Support nested builder in DSL for reactive apps

Fixes: gh-7107

samples/boot/oauth2webclient-webflux/src/main/java/sample/config/SecurityConfig.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 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.
@@ -23,6 +23,8 @@ 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
  */
@@ -32,15 +34,14 @@ public class SecurityConfig {
 	@Bean
 	SecurityWebFilterChain configure(ServerHttpSecurity http) throws Exception {
 		http
-			.authorizeExchange()
-				.pathMatchers("/", "/public/**").permitAll()
-				.anyExchange().authenticated()
-				.and()
-			.oauth2Login()
-				.and()
-			.formLogin()
-				.and()
-			.oauth2Client();
+			.authorizeExchange(exchanges ->
+				exchanges
+					.pathMatchers("/", "/public/**").permitAll()
+					.anyExchange().authenticated()
+			)
+			.oauth2Login(withDefaults())
+			.formLogin(withDefaults())
+			.oauth2Client(withDefaults());
 		return http.build();
 	}