add @ResponseBody Annotation to whoami action

src/main/java/de/thm/arsnova/LoginController.java

@@ -46,6 +46,7 @@ import org.springframework.stereotype.Controller;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RequestMethod;
 import org.springframework.web.bind.annotation.RequestParam;
+import org.springframework.web.bind.annotation.ResponseBody;
 import org.springframework.web.servlet.ModelAndView;
 import org.springframework.web.servlet.View;
 import org.springframework.web.servlet.view.RedirectView;
@@ -110,6 +111,7 @@ public class LoginController {
 	}
 
 	@RequestMapping(method = RequestMethod.GET, value = "/whoami")
+	@ResponseBody
 	public User whoami() {
 		return userService.getUser(SecurityContextHolder.getContext().getAuthentication());
 	}