SF4 + doctrine event - php

Question

I'm playing new Symfony 4. I really like when service use autowire and the component use annotations. I don't must nothing registration in services.yml. Ofcourse I can't solve everything in this way, but I try.
I create simple and test project. When I have Page. Page has "slug" field. This value is generated with field "title". I created special service (App\Service\Slug).
I would like to generate slug in event when page is create or update. To the event I should be to injected the slug service.
I would like to create one listner for only one entity - Page. I found: https://symfony.com/doc/current/doctrine/event_listeners_subscribers.html In this solution the event is run for all entities and I must create configuration in services.yml.
App\EventListener\PageListener:
tags:
- { name: doctrine.event_listener, event: prePersist }
class PageListener
{
/**
* #var Slug
*/
protected $slug;
/**
* PageListener constructor.
*
* #param Slug $slug
*/
public function __construct(Slug $slug)
{
$this->slug = $slug;
}
public function prePersist(
LifecycleEventArgs $args
) {
$page = $args->getObject();
/** ... */
$slug = $this->slug->get($page->getTitle());
$page->setSlug($slug);
/** ... */
}
}
In this solution the event is run in all enitites and I must check the instance.
I remeber that In sf2.8 I could add adnotation to entity (EntityListeners) -> https://www.doctrine-project.org/projects/doctrine-orm/en/latest/reference/events.html In this version symfony I see this adnotation but it doesn't work. I found only old cookbook: https://symfony.com/doc/master/bundles/DoctrineBundle/entity-listeners.html
How should I do it correctly?
In the conclusion I want to create a simple doctrine event, which work for only one entity and its configuration is minimal.
edit:
When I tested, I found solution which "works":
Entity:
/**
* Class Page
*
* #package App\Entity
*
* #ORM\Entity(repositoryClass="App\Repository\ProductRepository")
* #ORM\EntityListeners("App\EventListener\PageListener")
* #ORM\Table(name="pages")
*/
class Page
services.yaml:
App\EventListener\PageListener:
tags:
- { name: doctrine.orm.entity_listener }
PageListener:
public function __construct(Slug $slug)
{
$this->slug = $slug;
}
/**
* #ORM\PrePersist
*/
public function prePersistHandler(Page $user, LifecycleEventArgs $event)
I don't know how or I can't removed configuration in "service.yaml".