AsyncAWS - visibilityConverter should be a service

doc/adapter_async_aws_s3.md

@@ -7,6 +7,9 @@ the S3 client at [async-aws.com](https://async-aws.com/clients/) or use the
 
 ```yml
 services:
+    acme.async.portable_visibility_converter:
+        class: League\Flysystem\AsyncAwsS3\PortableVisibilityConverter:
+
     acme.async_s3_client:
         class: AsyncAws\S3\S3Client
         arguments:
@@ -25,6 +28,8 @@ oneup_flysystem:
                 client: acme.async_s3_client
                 bucket: 'my_image_bucket'
                 prefix: ''
+                visibilityConverter: acme.async.portable_visibility_converter
+
 ```
 
 ## More to know

src/DependencyInjection/Factory/Adapter/AsyncAwsS3Factory.php

@@ -19,12 +19,14 @@ public function getKey(): string
 
     public function create(ContainerBuilder $container, string $id, array $config): void
     {
+        $visibilityConverter = $config['visibilityConverter'] ? new Reference($config['visibilityConverter']) : null;
+
         $container
             ->setDefinition($id, new ChildDefinition('oneup_flysystem.adapter.async_aws_s3'))
             ->replaceArgument(0, new Reference($config['client']))
             ->replaceArgument(1, $config['bucket'])
             ->replaceArgument(2, $config['prefix'])
-            ->replaceArgument(3, $config['visibilityConverter'])
+            ->replaceArgument(3, $visibilityConverter)
         ;
     }