Update best_practices.rst

[amine-betari]

// there is a public "router" service in the container
$router = $this->container->get('router');

// this will not Work: MailLogger is a private service
$mailLogger = $this->container->get(MailLogger::class);

[javiereguiluz]

@amine-betari thanks! This is correct ... but the reword implies that you can access to ALL public services, and that's not true. So ... what if reword this again and say something like this:

If you extend the base ``AbstractController``, you can only access to
the most common services (e.g. ``twig``, ``router``, ``doctrine``, etc.).
via ``$this->container->get()`` or ``$this->get()``. Use dependency
injection to fetch the rest of services [...]

[amine-betari]

@javiereguiluz done

thank's. I thought we could access to all public services

[OskarStark]

I am going to merge it

[OskarStark]

Thank you @amine-betari.