#728 - Add support for Spring WebFlux.

* Render hypermedia from WebFlux controllers.
* Support consuming hypermedia through WebClient.
* Support link creation reactively with a custom filter and explicitly with a user-provided ServerWebExchange.
* Add a ReactiveResourceAssembler and SimpleReactiveResourceAssembler.
* Upgrade to Spring Framework 5.2 to align with Spring Data Moore, removing specialized Forwarded header handling.

Author: gregturn

pom.xml

@@ -13,7 +13,7 @@
 		hyper-text driven REST web services.
 	</description>
 
-	<inceptionYear>2012-2018</inceptionYear>
+	<inceptionYear>2012-2019</inceptionYear>
 
 	<organization>
 		<name>Pivotal, Inc.</name>
@@ -48,7 +48,7 @@
 			<name>Apache License, Version 2.0</name>
 			<url>http://www.apache.org/licenses/LICENSE-2.0</url>
 			<comments>
-			Copyright 2011-2018 the original author or authors.
+			Copyright 2011-2019 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.
@@ -77,6 +77,7 @@
 		<java-module-name>spring.hateoas</java-module-name>
 		<jsonpath.version>2.2.0</jsonpath.version>
 		<minidevjson.version>2.2.1</minidevjson.version>
+		<reactor-bom.version>Californium-SR4</reactor-bom.version>
 		<slf4j.version>1.7.25</slf4j.version>
 		<spring.version>5.1.5.RELEASE</spring.version>
 		<spring-plugin.version>2.0.0.BUILD-SNAPSHOT</spring-plugin.version>
@@ -434,6 +435,18 @@
 
 	</profiles>
 
+	<dependencyManagement>
+		<dependencies>
+			<dependency>
+				<groupId>io.projectreactor</groupId>
+				<artifactId>reactor-bom</artifactId>
+				<version>${reactor-bom.version}</version>
+				<scope>import</scope>
+				<type>pom</type>
+			</dependency>
+		</dependencies>
+	</dependencyManagement>
+
 	<dependencies>
 
 		<!-- Kotlin extension -->
@@ -490,6 +503,14 @@
 			<groupId>org.springframework</groupId>
 			<artifactId>spring-webmvc</artifactId>
 			<version>${spring.version}</version>
+			<optional>true</optional>
+		</dependency>
+
+		<dependency>
+			<groupId>org.springframework</groupId>
+			<artifactId>spring-webflux</artifactId>
+			<version>${spring.version}</version>
+			<optional>true</optional>
 		</dependency>
 
 		<dependency>
@@ -595,6 +616,24 @@
 			<scope>test</scope>
 		</dependency>
 
+		<dependency>
+			<groupId>io.projectreactor.netty</groupId>
+			<artifactId>reactor-netty</artifactId>
+			<scope>test</scope>
+		</dependency>
+
+		<dependency>
+			<groupId>io.projectreactor</groupId>
+			<artifactId>reactor-test</artifactId>
+			<scope>test</scope>
+		</dependency>
+
+		<dependency>
+			<groupId>io.projectreactor.addons</groupId>
+			<artifactId>reactor-extra</artifactId>
+			<scope>test</scope>
+		</dependency>
+		
 		<!--  Needs to be after Jadler to make sure it sees the Servlet 3.0 dependency pulled in for testing -->
 
 		<dependency>

src/main/java/org/springframework/hateoas/ResourceSupport.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2018 the original author or authors.
+ * Copyright 2012-2019 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.
@@ -41,6 +41,22 @@ public ResourceSupport() {
 		this.links = new ArrayList<>();
 	}
 
+	public ResourceSupport(Link initialLink) {
+
+		Assert.notNull(initialLink, "initialLink must not be null!");
+
+		this.links = new ArrayList<>();
+		this.links.add(initialLink);
+	}
+
+	public ResourceSupport(List<Link> initialLinks) {
+
+		Assert.notNull(initialLinks, "initialLinks must not be null!");
+
+		this.links = new ArrayList<>();
+		this.links.addAll(initialLinks);
+	}
+
 	/**
 	 * Returns the {@link Link} with a rel of {@link IanaLinkRelations#SELF}.
 	 */

src/main/java/org/springframework/hateoas/config/ConverterRegisteringWebMvcConfigurer.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2015-2018 the original author or authors.
+ * Copyright 2015-2019 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.
@@ -16,7 +16,6 @@
 package org.springframework.hateoas.config;
 
 import org.springframework.beans.factory.BeanCreationException;
-import org.springframework.beans.factory.ObjectFactory;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Primary;
@@ -39,6 +38,7 @@
  * Common HATEOAS specific configuration.
  *
  * @author Oliver Gierke
+ * @author Greg Turnquist
  * @soundtrack Elephants Crossing - Wait (Live at Stadtfest Dresden)
  * @since 0.19
  */
@@ -66,12 +66,6 @@ public MessageSourceAccessor linkRelationMessageSource() {
 		}
 	}
 
-	@Bean
-	ConverterRegisteringBeanPostProcessor jackson2ModuleRegisteringBeanPostProcessor(
-			ObjectFactory<ConverterRegisteringWebMvcConfigurer> configurer) {
-		return new ConverterRegisteringBeanPostProcessor(configurer);
-	}
-
 	// RelProvider
 
 	@Bean