Fix permission logic priorities

This helps to fix a bug in flarum-ext-tags where a user could not rename or edit the tags of their own discussion if it was in a restricted tag. This was due to the order of GetPermission event listeners – the logic that determines that a user *can't* perform an action because of a restrictive tag was running before (and thus instead of) the logic that determines that a user *can* edit their own stuff.

The solution is to change the "catch-all" methods on Policies to "after" instead of "before" – that is, they will run only if the per-ability methods return null.

We also simplify the GetPermission event by passing the model as a sole "argument", as I can't imagine any cases where we'll need more than one argument.

src/Event/GetPermission.php

@@ -25,19 +25,19 @@ class GetPermission
     public $ability;
 
     /**
-     * @var array
+     * @var mixed
      */
-    public $arguments;
+    public $model;
 
     /**
      * @param User $actor
      * @param string $ability
-     * @param array $arguments
+     * @param mixed $model
      */
-    public function __construct(User $actor, $ability, array $arguments)
+    public function __construct(User $actor, $ability, $model)
     {
         $this->actor = $actor;
         $this->ability = $ability;
-        $this->arguments = $arguments;
+        $this->model = $model;
     }
 }