Missing thumbnails for private attachments in Media library

[mklasen]

Heya!

I noticed private attachment thumbnails are not showing when the Media library is shown in (default) grid view. I've solved this on my own environment with the following snippet;

add_filter( 'wp_prepare_attachment_for_js', array( $this, 'prepare_js_attachments' ) );

	public function prepare_js_attachments( $attachment ) {
		$s3_uploads = \S3_Uploads\Plugin::get_instance();
		if ( $s3_uploads->is_private_attachment( $attachment['id'] ) ) {
			if ( isset( $attachment['sizes'] ) && is_array( $attachment['sizes'] ) ) {
				foreach ( $attachment['sizes'] as &$size ) {
					$size['url'] = $s3_uploads->add_s3_signed_params_to_attachment_url( $size['url'], $attachment['id'] );
				}
			}
		}
		return $attachment;
	}

Happy to provide a PR :)