[4.x] entity_reference parent's language

nested Entity loaded via entity reference field come in the default language, not in the current language, meaning the language of the parent.
I can't find a way to get the right language from entity_reference.

```gql
type Article implements NodeInterface {
...
linked_materials: [Materiau]
...
}
type Materiau implements NodeInterface {
id: Int!
uuid: String!
title: String!
...
}
```

```php
$registry->addFieldResolver('Article', 'linked_materials',
$builder->produce('entity_reference')
->map('entity', $builder->fromParent())
->map('field', $builder->fromValue('field_linked_materials'))
);
```

where i am now with my try
``` php
$registry->addFieldResolver('Article', 'linked_materials',
$builder->compose(
$builder->callback(function($parent, $args){
$linkedmaterials = $parent->get('field_linked_materials')->getValue();
$nids = [];
foreach ($linkedmaterials as $key => $value) {
$nids[] = $value['target_id'];
}
$lang = $parent->language()->getId();
// return [
// "ids" => $nids,
// "language" => $lang
// ];
return $nids;
}),
$builder->produce('entity_load_multiple')
->map('type', $builder->fromValue('node'))
->map('bundles', $builder->fromValue(['materiau']))
->map('ids', $builder->fromParent())
->map('language', $builder->fromValue('fr')) // hard coded language working, how can i transmit the language from the parent ?
)
);
```