ALF-9153 Avoid fetching too much un-used data when rendering a Discussions Topic to JSON with the reply count

git-svn-id: https://svn.alfresco.com/repos/alfresco-enterprise/alfresco/HEAD/root@29773 c4b6b30b-aa2e-2d43-bbcb-ca4b014f7261

source/java/org/alfresco/service/cmr/discussion/DiscussionService.java

@@ -124,6 +124,17 @@ public interface DiscussionService {
    @NotAuditable
    PostInfo getPrimaryPost(TopicInfo topic);
    
+   /**
+    * Retrieves the newest (most recent) Post in a topic, be that 
+    *  the Primary Post or a Reply.
+    * This is typically used when identifying if a topic has had
+    *  new posts added to it since the user last saw it.
+    * Note that this works on Created Date, and not Modified/Updated,
+    *  so edits to an existing post will not change this.
+    */
+   @NotAuditable
+   PostInfo getMostRecentPost(TopicInfo topic);
+   
    /**
     * Retrieves an existing {@link TopicInfo} from the repository,
     *  which is within a site