FestinHegre/templates/clients/_delete_form.html.twig

<form method="post" action="{{ path('app_clients_delete', {'id': client.id}) }}" onsubmit="return confirm('Es-tu sur de vouloir le supprimer ?');">
    <input type="hidden" name="_token" value="{{ csrf_token('delete' ~ client.id) }}">
    <button class="btn">Supprimer</button>
</form>