Use new extenders (#23)

extensions/approval/extend.php

@@ -7,6 +7,8 @@
  * LICENSE file that was distributed with this source code.
  */
 
+use Flarum\Api\Serializer\BasicDiscussionSerializer;
+use Flarum\Api\Serializer\PostSerializer;
 use Flarum\Approval\Access;
 use Flarum\Approval\Listener;
 use Flarum\Discussion\Discussion;
@@ -30,10 +32,21 @@ return [
     (new Extend\Model(Post::class))
         ->default('is_approved', true),
 
+    (new Extend\ApiSerializer(BasicDiscussionSerializer::class))
+        ->attribute('isApproved', function ($serializer, Discussion $discussion) {
+            return (bool) $discussion->is_approved;
+        }),
+
+    (new Extend\ApiSerializer(PostSerializer::class))
+        ->attribute('isApproved', function ($serializer, Post $post) {
+            return (bool) $post->is_approved;
+        })->attribute('canApprove', function (PostSerializer $serializer, Post $post) {
+            return (bool) $serializer->getActor()->can('approvePosts', $post->discussion);
+        }),
+
     new Extend\Locales(__DIR__.'/locale'),
 
     function (Dispatcher $events) {
-        $events->subscribe(Listener\AddPostApprovalAttributes::class);
         $events->subscribe(Listener\ApproveContent::class);
         $events->subscribe(Listener\UnapproveNewContent::class);