add server-side code and mobile app code

server/vendor/symfony/mime/HtmlToTextConverter/DefaultHtmlToTextConverter.php

@@ -0,0 +1,23 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Mime\HtmlToTextConverter;
+
+/**
+ * @author Fabien Potencier <fabien@symfony.com>
+ */
+class DefaultHtmlToTextConverter implements HtmlToTextConverterInterface
+{
+    public function convert(string $html, string $charset): string
+    {
+        return strip_tags(preg_replace('{<(head|style)\b.*?</\1>}is', '', $html));
+    }
+}