All post types get numbers

Decided this is necessary because some notifications will need to link
to posts which are not comments (e.g. a “renamed” post)

src/Core/Models/CommentPost.php

@@ -15,22 +15,6 @@ class CommentPost extends Post
      */
     protected static $formatter;
 
-    /**
-     * Add an event listener to set the post's number, and update the
-     * discussion's number index, when inserting a post.
-     *
-     * @return void
-     */
-    public static function boot()
-    {
-        parent::boot();
-
-        static::creating(function ($post) {
-            $post->number = ++$post->discussion->number_index;
-            $post->discussion->save();
-        });
-    }
-
     /**
      * Create a new instance in reply to a discussion.
      *

src/Core/Models/Post.php

@@ -47,7 +47,9 @@ class Post extends Model
     protected static $types = [];
 
     /**
-     * Raise an event when a post is deleted.
+     * Raise an event when a post is deleted. Add an event listener to set the
+     * post's number, and update the discussion's number index, when inserting
+     * a post.
      *
      * @return void
      */
@@ -55,6 +57,11 @@ class Post extends Model
     {
         parent::boot();
 
+        static::creating(function ($post) {
+            $post->number = ++$post->discussion->number_index;
+            $post->discussion->save();
+        });
+
         static::deleted(function ($post) {
             $post->raise(new PostWasDeleted($post));
         });