feat: stub DataMapperInterface

Ensure TData of FormInterface is provided Set TData on mixed since we don't know the type of the child forms Add template for in DataMapperInterface refs: #417

stubs/Symfony/Component/Form/DataMapperInterface.sub

@@ -0,0 +1,21 @@
+<?php
+
+namespace Symfony\Component\Form;
+
+/**
+ * @template TViewData
+ */
+interface DataMapperInterface
+{
+ /**
+ * @param TViewData $viewData
+ * @param \Traversable<mixed, FormInterface<mixed>> $forms
+ */
+ public function mapDataToForms(mixed $viewData, \Traversable $forms): void;
+
+ /**
+ * @param \Traversable<mixed, FormInterface<mixed>> $forms
+ * @param TViewData $viewData
+ */
+ public function mapFormsToData(\Traversable $forms, mixed &$viewData): void;
+}