Added shortUrl field to serialized ShortUrl objects, both from CLI and REST

module/Common/src/Rest/DataTransformerInterface.php

@@ -0,0 +1,9 @@
+<?php
+declare(strict_types=1);
+
+namespace Shlinkio\Shlink\Common\Rest;
+
+interface DataTransformerInterface
+{
+    public function transform($value): array;
+}