Symfony EasyAdminBundle: Creating a custom crud action to save a csv

I am following this tutorial here. I would like to create a custom action that saves a csv file. I want to save my user class, but for now I just want to understand why the function saveUsersToCsv is not being called. Here is my UserCrudController:

UserCrudController.php

<?php

namespace App\Controller\Admin;

use EasyCorp\Bundle\EasyAdminBundle\Field\TextField;
use EasyCorp\Bundle\EasyAdminBundle\Field\EmailField;
use EasyCorp\Bundle\EasyAdminBundle\Config\Actions;
use EasyCorp\Bundle\EasyAdminBundle\Config\Action;
use EasyCorp\Bundle\EasyAdminBundle\Config\Crud;
use EasyCorp\Bundle\EasyAdminBundle\Context\AdminContext;
use App\Entity\User;
use EasyCorp\Bundle\EasyAdminBundle\Controller\AbstractCrudController;
use EasyCorp\Bundle\EasyAdminBundle\Field\ArrayField;

class UserCrudController extends AbstractCrudController
{
    public static function getEntityFqcn(): string
    {
        return User::class;
    }

    // configurable fields
    // see: https://symfony.com/bundles/EasyAdminBundle/current/fields.html
    public function configureFields(string $pageName): iterable
    {
        return [
            TextField::new("username"),
            EmailField::new('email'),
            ArrayField::new('roles'),
        ];
    }
    public function configureActions(Actions $actions): Actions
    {
        $saveCsv = Action::new('saveCsv','Save as Csv', 'fa fa-save-as-csv')
            ->displayAsButton()
            ->linkToCrudAction('saveUsersToCsv');

        return $actions
            ->add(Crud::PAGE_DETAIL,$saveCsv);
    }
    // https://stackoverflow.com/questions/27888374/create-csv-and-force-download-of-file
    public function saveUsersToCsv(AdminContext $context){
        // $instance = $context->getEntity()->getInstance();

        $fileName = "test";
        $filePath = $_SERVER["DOCUMENT_ROOT"] . $fileName . '.csv';
        $output = fopen($filePath,'w+');
        fputcsv($output,array("Number","Description","test"));
        fputcsv($output,array("100","TestDescription","10"));

        // set the headers
        header('Content-Type: application/octet-stream');
        header('Content-Disposition: attachment; filename ="'.$fileName.".csv'");
        header('Content-Length: ' .filesize($filePath));
        echo readfile($filePath);
    }
}

The button for saving a user does correctly show up, but when clicked nothing happens:

How can I get the button click to call the function to save the csv file?

I have found a solution. Here is the code in UserCrudController.php.

<?php

namespace App\Controller\Admin;

namespace App\Controller\Admin;

use App\Entity\Product;
use Doctrine\ORM\EntityManagerInterface;
use Doctrine\ORM\QueryBuilder;
use EasyCorp\Bundle\EasyAdminBundle\Config\Action;
use EasyCorp\Bundle\EasyAdminBundle\Config\Actions;
use EasyCorp\Bundle\EasyAdminBundle\Config\Crud;
use EasyCorp\Bundle\EasyAdminBundle\Context\AdminContext;
use EasyCorp\Bundle\EasyAdminBundle\Controller\AbstractCrudController;
use EasyCorp\Bundle\EasyAdminBundle\Field\AssociationField;
use EasyCorp\Bundle\EasyAdminBundle\Field\BooleanField;
use EasyCorp\Bundle\EasyAdminBundle\Field\DateTimeField;
use EasyCorp\Bundle\EasyAdminBundle\Field\IdField;
use EasyCorp\Bundle\EasyAdminBundle\Field\ImageField;
use EasyCorp\Bundle\EasyAdminBundle\Field\MoneyField;
use EasyCorp\Bundle\EasyAdminBundle\Field\TextEditorField;
use EasyCorp\Bundle\EasyAdminBundle\Field\TextField;
use EasyCorp\Bundle\EasyAdminBundle\Field\ArrayField;
use EasyCorp\Bundle\EasyAdminBundle\Field\EmailField;
use EasyCorp\Bundle\EasyAdminBundle\Router\AdminUrlGenerator;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\HttpFoundation\StreamedResponse;

use App\Entity\User;

class UserCrudController extends AbstractCrudController
{
    public const ACTION_SAVE_CSV = "SAVE_CSV";

    // entity manager
    private $em;

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

    public static function getEntityFqcn(): string
    {
        return User::class;
    }

    // configurable fields
    // see: https://symfony.com/bundles/EasyAdminBundle/current/fields.html
    public function configureFields(string $pageName): iterable
    {
        return [
            TextField::new("username"),
            EmailField::new('email'),
            ArrayField::new('roles'),
        ];
    }
    public function configureActions(Actions $actions): Actions
    {
        $duplicate = Action::new(self::ACTION_SAVE_CSV)
            ->linkToCrudAction('saveUsersToCsv')
            ->setCssClass('btn btn-info')
            ->createAsGlobalAction();

        return $actions
            ->add(Crud::PAGE_INDEX,$duplicate);
    }

    public function saveUsersToCsv(
        AdminContext $context,
        AdminUrlGenerator $adminUrlGenerator,
        EntityManagerInterface $em
    ): Response {

        $userRepo = $this->em->getRepository(User::class);
        $users= $userRepo->findAll(); // Doctrine query
        $rows = array();
        $columns = array(
            'id',
            'email',
        );
        $rows[] = implode(',',$columns);
        foreach($users as $user){
            $data = array(
                $user->getId(),
                $user->getEmail(),
            );
            $rows[] = implode(',',$data);
        }
        $content = implode("\n",$rows);
        $response = new Response($content);
        $response->headers->set("Content-Type",'text/csv');
        $response->headers->set("Content-Disposition",'attachment; filename="users.csv"');

        return $response;
    }
}

The main problem was that I was not passing in the right arguments into the action function, and that I did not know at the time how to create a correct response.