[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/Blog/Controller/Post.php

@@ -145,7 +145,7 @@ class Post extends Controller
                         content_type: $content_type,
                         locale: $data['language'],
                         scope: VisibilityScope::from($data['visibility']),
-                        targets: [(int) $data['in']],
+                        attentions: [(int) $data['in']],
                         reply_to: $data['reply_to_id'],
                         attachments: $data['attachments'],
                         process_note_content_extra_args: $extra_args,