feed controller: add cache control for feed result

http-service/src/main/java/net/runelite/http/service/feed/FeedController.java

@@ -27,6 +27,7 @@ package net.runelite.http.service.feed;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.concurrent.TimeUnit;
 import lombok.extern.slf4j.Slf4j;
 import net.runelite.http.api.feed.FeedItem;
 import net.runelite.http.api.feed.FeedResult;
@@ -34,6 +35,8 @@ import net.runelite.http.service.feed.blog.BlogService;
 import net.runelite.http.service.feed.osrsnews.OSRSNewsService;
 import net.runelite.http.service.feed.twitter.TwitterService;
 import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.http.CacheControl;
+import org.springframework.http.ResponseEntity;
 import org.springframework.scheduling.annotation.Scheduled;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RestController;
@@ -93,8 +96,16 @@ public class FeedController
 	}
 
 	@RequestMapping
-	public FeedResult getFeed()
+	public ResponseEntity<FeedResult> getFeed()
 	{
-		return feedResult;
+		if (feedResult == null)
+		{
+			return ResponseEntity.notFound()
+				.build();
+		}
+
+		return ResponseEntity.ok()
+			.cacheControl(CacheControl.maxAge(10, TimeUnit.MINUTES).cachePublic())
+			.body(feedResult);
 	}
 }