Multi-filter doesn't work with vichUploaderField

[Koronos]

Using the next example:

	/**
	 * @Vich\UploadableField(mapping="files", fileNameProperty="fileName", size="fileSize")
	 * @Serializer\Exclude()
	 *
	 * @var \Symfony\Component\HttpFoundation\File\File|null
	 */
    private $file;

    /**
     * @ORM\Column(type="string", length=255, nullable=true)
	 * @Serializer\SerializedName("file")
	 *
	 * @LiipImagineSerializableField(filter={"api_img","api_thumb"}, vichUploaderField="file")
     */
    private $fileName;

When I use a single filter it works perfectly:

@LiipImagineSerializableField("api_img", vichUploaderField="file")

But I use more than 1 filter, I got an Array to string conversion error in JMS

at K:\wamp64\www\refaccionariaCentro\vendor\jms\serializer\src\GraphNavigator\SerializationGraphNavigator.php:144
at JMS\Serializer\GraphNavigator\SerializationGraphNavigator->accept(array('api_img' => 'http://localhost:8000/media/cache/resolve/api_img/files/153825169-150412593593858-1896732942807405473-n-603ffab9beae2505028842.png', 'api_thumb' => 'http://localhost:8000/media/cache/resolve/api_thumb/files/153825169-150412593593858-1896732942807405473-n-603ffab9beae2505028842.png'), array('name' => 'string', 'params' => array()))

For the moment it can be fixed adding the @Serializer\Type("array") annotation to the field when are used more than 1 filter. The strange is that in a string field, is not necessary.

Suggestion:

The limp annotation should set is as array when is added more than 1 filter as it does when is a string property. Or almost should be added this info to the docs.

Regards.

[Bukashk0zzz]

Thanks for the issue with the detailed description.
Not sure that I will have time to fix this soon, but pull requests are welcome.