Replace @Controller with @RestController

See gh-1401

initializr-web/src/main/java/io/spring/initializr/web/controller/CommandLineMetadataController.java

@@ -39,7 +39,7 @@ import org.springframework.web.bind.annotation.RequestMapping;
  *
  * @author Stephane Nicoll
  */
-@Controller
+@RestController
 public class CommandLineMetadataController extends AbstractMetadataController {
 
 	private final CommandLineHelpGenerator commandLineHelpGenerator;

initializr-web/src/main/java/io/spring/initializr/web/controller/ProjectGenerationController.java

@@ -65,7 +65,7 @@ import org.springframework.web.bind.annotation.RequestParam;
  * @param <R> the {@link ProjectRequest} type to use to bind request parameters
  * @author Stephane Nicoll
  */
-@Controller
+@RestController
 public abstract class ProjectGenerationController<R extends ProjectRequest> {
 
 	private static final Log logger = LogFactory.getLog(ProjectGenerationController.class);

initializr-web/src/main/java/io/spring/initializr/web/controller/ProjectMetadataController.java

@@ -50,7 +50,7 @@ import org.springframework.web.bind.annotation.ResponseBody;
  *
  * @author Stephane Nicoll
  */
-@Controller
+@RestController
 public class ProjectMetadataController extends AbstractMetadataController {
 
 	/**
@@ -67,7 +67,6 @@ public class ProjectMetadataController extends AbstractMetadataController {
 	}
 
 	@RequestMapping(path = "/metadata/config", produces = "application/json")
-	@ResponseBody
 	public InitializrMetadata config() {
 		return this.metadataProvider.get();
 	}

initializr-web/src/main/java/io/spring/initializr/web/controller/SpringCliDistributionController.java

@@ -26,7 +26,7 @@ import org.springframework.web.bind.annotation.RequestMapping;
  *
  * @author Stephane Nicoll
  */
-@Controller
+@RestController
 public class SpringCliDistributionController {
 
 	private final InitializrMetadataProvider metadataProvider;