Make traits more generic

Type hinting User should take place in the callbacks. Theoretically
these traits could be used for another project now, where something
else has permissions (like a Sheep class, or a number)

src/Extend/Model.php

@@ -82,7 +82,7 @@ class Model implements ExtenderInterface
         }
 
         foreach ($this->scopeVisible as $callback) {
-            $model::scopeVisible($callback);
+            $model::addVisiblePostsScope($callback);
         }
 
         foreach ($this->allow as $info) {