[COMPONENT][Notification] Make logic more generic and robust

Fixed various bugs

Some important concepts to bear in mind:

* Notification: Associated with activities, won't be reconstructed
together with objects, can be thought of as transient

* Attention: Associated with objects, will be reconstructed with them, can
be thought as persistent

* Notifications and Attentions have no direct implications.

* Mentions are a specific form of attentions in notes, leads to the creation of Attentions.

Finally,

Potential PHP issue detected and reported: https://github.com/php/php-src/issues/8199
`static::method()` from a non static context (such as a class method) calls `__call`, rather than
the expected `__callStatic`. Can be fixed by using `(static fn() => static::method())()`, but the
usage of the magic method is strictly unnecessary in this case.

components/Notification/Controller/Feed.php

@@ -53,9 +53,9 @@ class Feed extends Controller
             WHERE n.id IN (
                 SELECT act.object_id FROM \App\Entity\Activity AS act
                     WHERE act.object_type = 'note' AND act.id IN
-                        (SELECT att.activity_id FROM \Component\Notification\Entity\Notification AS att WHERE att.target_id = :id)
+                        (SELECT att.activity_id FROM \Component\Notification\Entity\Notification AS att WHERE att.target_id = :target_id)
                 )
-            EOF, ['id' => $user->getId()]);
+            EOF, [':target' => $user->getId()]);
         return [
             '_template'     => 'collection/notes.html.twig',
             'page_title'    => _m('Notifications'),