Add the `mail_settings` field to the payload when using `symfony/sendgrid-mailer`

framework.yaml

framework:
  http_client:
    scoped_clients:
      sendgrid.client:
        base_uri: 'https://api.sendgrid.com'

Kernel.php

<?php

declare(strict_types=1);

namespace App;

use App\HttpClient\SendgridHttpClient;
use Symfony\Bundle\FrameworkBundle\Kernel\MicroKernelTrait;
use Symfony\Component\DependencyInjection\Compiler\CompilerPassInterface;
use Symfony\Component\DependencyInjection\ContainerBuilder;
use Symfony\Component\HttpKernel\Kernel as BaseKernel;

final class Kernel extends BaseKernel implements CompilerPassInterface
{
    use MicroKernelTrait;

    public function process(ContainerBuilder $container)
    {
        // Injects the `SendgridHttpClient` decorator instead of the default HTTP Client.
        // It adds the `mail_settings` field to the payload.
        // @see: App\HttpClient\SendgridHttpClient
        $container
            ->getDefinition('mailer.transport_factory.sendgrid')
            ->setArgument('$client', $container->getDefinition(SendgridHttpClient::class))
        ;
    }
}

SendgridHttpClient.php

<?php

declare(strict_types=1);

namespace App\HttpClient;

use Symfony\Component\DependencyInjection\Attribute\AsDecorator;
use Symfony\Component\DependencyInjection\Attribute\MapDecorated;
use Symfony\Component\Mailer\Bridge\Sendgrid\Transport\SendgridApiTransport;
use Symfony\Contracts\HttpClient\HttpClientInterface;
use Symfony\Contracts\HttpClient\ResponseInterface;
use Symfony\Contracts\HttpClient\ResponseStreamInterface;
use function json_encode;

/**
 * Decorates the Sendgrid scoped client to add the `mail_settings` field to the payload.
 *
 * @see SendgridApiTransport
 */
#[AsDecorator('sendgrid.client')]
class SendgridHttpClient implements HttpClientInterface
{
    public function __construct(#[MapDecorated] private readonly HttpClientInterface $inner)
    {
    }

    public function request(string $method, string $url, array $options = []): ResponseInterface
    {
        $options['json']['mail_settings'] = [
            'bypass_unsubscribe_management' => ['enable' => true],
        ];

        return $this->inner->request($method, $url, $options);
    }

    public function stream(iterable|ResponseInterface $responses, ?float $timeout = null): ResponseStreamInterface
    {
        return $this->inner->stream($responses, $timeout);
    }

    public function withOptions(array $options): static
    {
        return new self($this->inner->withOptions($options));
    }
}