Add ObjectToArrayTransformerInterface with an automatic implementation

Transformer/ObjectToArrayTransformerInterface.php

@@ -0,0 +1,15 @@
+<?php
+
+namespace FOQ\ElasticaBundle\Transformer;
+
+interface ObjectToArrayTransformerInterface
+{
+    /**
+     * Transforms an object into an array having the required keys
+     *
+     * @param object $object the object to convert
+     * @param array $requiredKeys the keys we want to have in the returned array
+     * @return array
+     **/
+    public function transform($object, array $requiredKeys);
+}