symfony4, api-platform upload file : Format "multipart/form-data" is not supported

I would like to do an API with symfony 4, api-platform which allow to upload file and run a system commande with it and delete it. I want use in a controle somethink like :

$uploadedConfig = $request->files->get('cfgfile');
exec("mycall ".$uploadedConfig->getPathname());

But I have the following errors : Format "multipart/form-data" is not supported

my test is :

curl -X POST -F 'cfgfile=/tmp/maconf' http://<IP>/api/config -H "Content-Type: multipart/form-data"

thanks Thomas