How does Laravel know about Middlewares of packages by auto discovery?

Searched for this information and I couldn't find anything. Only github links and some info but about service providers not middlewares.

I saw something about registering middlewares in service providers, but it's not the point.

I mean.

This package - laravel-page-speed

As I read, auto discovery takes registration of service providers from composer.json.

Okay, but there is no word about middlewares.

So maybe this package?

public function boot()
    {
        $this->publishes([
            __DIR__.'/../config/laravel-page-speed.php' => config_path('laravel-page-speed.php'),
        ]);
    }
    /**
     * Register the service provider.
     */
    public function register()
    {
        $this->mergeConfigFrom(__DIR__.'/../config/laravel-page-speed.php', 'laravel-page-speed.php');
    }

I don't see anything about middlewares, so maybe this config? I won't put here all the code, but too, nothing about it. Just enable package and skipped extensions.

So how?

This package uses and brings in several middlewares, but doesn't register them anywhere.

Without auto-discovery we need to type them on our own. But with auto discovery we haven't and I don't see anywhere in the package to register them.

So just I need explanation how this works.

How this middlewares actually are registered to work?

via Chebli Mohamed