Add support for Spring HATEOAS hypermedia in Actuator endpoints

If spring-hateoas is on the classpath and an MvcEndpoint returns a
@ResponseBody it will be extended and wrapped into a Resource with links.
All the existing endpoints that return sensible JSON data can be extended
this way (i.e. not /logfile). The HAL browser will also be added as an
endpoint if available on the classpath. Finally, asciidocs for the
Actuator endpoints are available as a separate jar file, which if
included in an app will also generate a new (HTTP) endpoint.

Fixes gh-1390

spring-boot-samples/spring-boot-sample-hypermedia-jpa/src/main/java/demo/Book.java

@@ -0,0 +1,35 @@
+/*
+ * Copyright 2015 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 demo;
+
+import javax.persistence.Entity;
+import javax.persistence.GeneratedValue;
+import javax.persistence.Id;
+
+@Entity
+public class Book {
+	@Id
+	@GeneratedValue
+	private Long id;
+	private String title;
+	public String getTitle() {
+		return this.title;
+	}
+	public void setTitle(String title) {
+		this.title = title;
+	}
+}

spring-boot-samples/spring-boot-sample-hypermedia-jpa/src/main/java/demo/BookRepository.java

@@ -0,0 +1,22 @@
+/*
+ * Copyright 2015 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 demo;
+
+import org.springframework.data.jpa.repository.JpaRepository;
+
+public interface BookRepository extends JpaRepository<Book, Long> {
+}

spring-boot-samples/spring-boot-sample-hypermedia-jpa/src/main/java/demo/JpaHypermediaApplication.java

@@ -0,0 +1,13 @@
+package demo;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class JpaHypermediaApplication {
+
+	public static void main(String[] args) {
+		SpringApplication.run(JpaHypermediaApplication.class, args);
+	}
+
+}

spring-boot-samples/spring-boot-sample-hypermedia-jpa/src/main/resources/application.properties

@@ -0,0 +1,2 @@
+management.contextPath=/admin
+endpoints.docs.curies.enabled=true