Add ConfigurableReactiveWebApplicationContext

Split the current `ReactiveWebApplicationContext` into two distinct
interfaces to mirror other Spring context interfaces. The
`ReactiveWebApplicationContext` interface now only exposes getters. The
`ConfigurableReactiveWebApplicationContext` exposes setters and extends
from `ConfigurableApplicationContext`.

Fixes gh-9794

spring-boot/src/main/java/org/springframework/boot/web/reactive/context/ConfigurableReactiveWebApplicationContext.java

@@ -0,0 +1,36 @@
+/*
+ * Copyright 2012-2017 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.web.reactive.context;
+
+import org.springframework.context.ConfigurableApplicationContext;
+
+/**
+ * Interface to provide configuration for a reactive web application.
+ *
+ * @author Stephane Nicoll
+ * @since 2.0.0
+ */
+public interface ConfigurableReactiveWebApplicationContext
+		extends ConfigurableApplicationContext, ReactiveWebApplicationContext {
+
+	/**
+	 * Set the namespace for this reactive web application context.
+	 * @param namespace the namespace for the context
+	 */
+	void setNamespace(String namespace);
+
+}

spring-boot/src/main/java/org/springframework/boot/web/reactive/context/GenericReactiveWebApplicationContext.java

@@ -33,8 +33,9 @@ import org.springframework.util.StringUtils;
  * @author Brian Clozel
  * @since 2.0.0
  */
-public class GenericReactiveWebApplicationContext extends
-		AnnotationConfigApplicationContext implements ReactiveWebApplicationContext {
+public class GenericReactiveWebApplicationContext
+		extends AnnotationConfigApplicationContext
+		implements ConfigurableReactiveWebApplicationContext {
 
 	private String namespace;
 

spring-boot/src/main/java/org/springframework/boot/web/reactive/context/ReactiveWebApplicationContext.java

@@ -26,12 +26,6 @@ import org.springframework.context.ApplicationContext;
  */
 public interface ReactiveWebApplicationContext extends ApplicationContext {
 
-	/**
-	 * Set the namespace for this reactive web application context.
-	 * @param namespace the namespace for the context
-	 */
-	void setNamespace(String namespace);
-
 	/**
 	 * Return the namespace for this reactive web application context, if any.
 	 * @return the namespace or {@code null}