Policy Extender and Tests (#2461)

Policy application has also been refactored, so that policies return one of `allow`, `deny`, `forceAllow`, `forceDeny`. The result of a set of policies is no longer the first non-null result, but rather the highest priority result (forceDeny > forceAllow > deny > allow, so if a single forceDeny is present, that beats out all other returned results). This removes order in which extensions boot as a factor.

src/Discussion/Access/DiscussionPolicy.php

@@ -7,38 +7,28 @@
  * LICENSE file that was distributed with this source code.
  */
 
-namespace Flarum\Discussion;
+namespace Flarum\Discussion\Access;
 
+use Flarum\Discussion\Discussion;
 use Flarum\Settings\SettingsRepositoryInterface;
-use Flarum\User\AbstractPolicy;
+use Flarum\User\Access\AbstractPolicy;
 use Flarum\User\User;
 use Illuminate\Contracts\Events\Dispatcher;
 
 class DiscussionPolicy extends AbstractPolicy
 {
-    /**
-     * {@inheritdoc}
-     */
-    protected $model = Discussion::class;
-
     /**
      * @var SettingsRepositoryInterface
      */
     protected $settings;
 
-    /**
-     * @var Dispatcher
-     */
-    protected $events;
-
     /**
      * @param SettingsRepositoryInterface $settings
      * @param Dispatcher $events
      */
-    public function __construct(SettingsRepositoryInterface $settings, Dispatcher $events)
+    public function __construct(SettingsRepositoryInterface $settings)
     {
         $this->settings = $settings;
-        $this->events = $events;
     }
 
     /**
@@ -49,7 +39,7 @@ class DiscussionPolicy extends AbstractPolicy
     public function can(User $actor, $ability)
     {
         if ($actor->hasPermission('discussion.'.$ability)) {
-            return true;
+            return $this->allow();
         }
     }
 
@@ -66,7 +56,7 @@ class DiscussionPolicy extends AbstractPolicy
             if ($allowRenaming === '-1'
                 || ($allowRenaming === 'reply' && $discussion->participant_count <= 1)
                 || ($discussion->created_at->diffInMinutes() < $allowRenaming)) {
-                return true;
+                return $this->allow();
             }
         }
     }
@@ -83,7 +73,7 @@ class DiscussionPolicy extends AbstractPolicy
             && (! $discussion->hidden_at || $discussion->hidden_user_id == $actor->id)
             && $actor->can('reply', $discussion)
         ) {
-            return true;
+            return $this->allow();
         }
     }
 }

src/Discussion/DiscussionServiceProvider.php

@@ -23,7 +23,6 @@ class DiscussionServiceProvider extends AbstractServiceProvider
         $events = $this->app->make('events');
 
         $events->subscribe(DiscussionMetadataUpdater::class);
-        $events->subscribe(DiscussionPolicy::class);
 
         $events->listen(
             Renamed::class,