Allow changing the URL in RenderAssetTagEvent

[pableu]

I have an application where it would be nice to modify the URL before rendering.

In my case, I want to change the URL based on the current request. E.g. if the user visits company.net I want to get the assets from media.company.net, and if the user visits shop.com, I want to get the assets from media.shop.com.

So far added my own twig functions that override the behavior of the default {{ encore_entry_script_tags }} and {{ encore_entry_style_tags }}, but I don't like that a lot.

Version 1.9.0 gave me an idea: What if we allowed to set a new URL to the RenderAssetTagEvent?

E.g. something like this:

<?php
declare(strict_types=1);

namespace App\EventSubscriber;

use Symfony\Component\EventDispatcher\EventSubscriberInterface;
use Symfony\WebpackEncoreBundle\Event\RenderAssetTagEvent;

class EncoreTagSubscriber implements EventSubscriberInterface
{
  public static function getSubscribedEvents()
  {
    return [
        RenderAssetTagEvent::class => 'onRenderAssetTag'
    ];
  }

  public function onRenderAssetTag(RenderAssetTagEvent $event)
  {
    // change URL according to our business logic
    $event->setUrl(str_replace('example.TLD', 'example.com', $event->getUrl()));
  }
}

This actually works like this, but it feels wrong and I need to set either src or href depending on type:

$event->setAttribute('src', str_replace('example.TLD', 'example.com', $event->getUrl()));

Would you be interested in a PR that adds the RenderAssetTagEvent::setUrl method? Or is my $event->setAttribute('src', ...); workaround okay and future proof?