FooController.php

<?php

class FooController
{
    public function indexAction(Request $request, UserData $userDataService): Response
    {
        $username = 'someuser';
      
        $foo = $userDataService->checkUser($username);
      
        if ($foo instanceof Response) {
          return $foo;
        }
      
        ....
    }
}

services.yml

services:
    AppBundle\Security\UserData:
        class: AppBundle\Security\UserData
        arguments: ['@doctrine.orm.entity_manager']

UserData.php

<?php

namespace AppBundle\Security;

use Doctrine\ORM\EntityManagerInterface;
use Symfony\Component\HttpFoundation\RedirectResponse;

class UserData
{
    private $entityManager;

    public function __construct(EntityManagerInterface $entityManager)
    {
        $this->entityManager = $entityManager;
    }

    public function checkUser($username)
    {
        $user = $this->entityManager->getRepository('AppBundle:User')->findOneBy(['username' => $username]);
        
        if ($user) {
            $camp = $this->entityManager->getRepository('AppBundle:Campaigns')->findOneBy(['id' => $user->getTarget()]);
            if ($camp) {
                // redirect
               return new return new RedirectResponse('https://www.facebook.com', 301);
            }
        }
        return true;
    }
}