API Enable comment specific enhancements

If an author creates a comment include a highlight class

_config/comments.yml

@@ -0,0 +1,8 @@
+---
+Name: blogcommentsconfig
+Only:
+  moduleexists: comments
+---
+Comment:
+  extensions:
+    - BlogCommentExtension

_config/config.yml

@@ -1,3 +1,6 @@
+---
+Name: blogconfig
+---
 Member:
   extensions:
-    - BlogMemberExtension
+    - BlogMemberExtension

code/extensions/BlogCommentExtension.php

@@ -0,0 +1,23 @@
+<?php
+
+/**
+ * Adds Blog specific behaviour to Comment
+ * Extends {@see Comment}
+ */
+class BlogCommentExtension extends DataExtension {
+
+	/**
+	 * Extra CSS classes for styling different comment types.
+	 * @return string
+	 */
+	public function getExtraClass() {
+		$blogPost = $this->owner->getParent();
+		
+		// Make sure we're dealing with a BlogPost.
+		if (  ($blogPost instanceof BlogPost)
+			&& $blogPost->isAuthor($this->owner->Author())
+		) {
+			return 'author-comment';
+		}
+	}
+}