Language: handle ui_lang via session

lib/modulekit/lang

@@ -1 +1 @@
-Subproject commit 78d341721cc5022b3a33827a870f792e9f19b7d0
+Subproject commit efeb19d26228b4b62ba5fdc6b16a911e350f6388

modulekit.php

@@ -12,6 +12,7 @@ $depend = array(
 $include = array(
   'php' => array(
     'src/options.php',
+    'src/language.php',
   ),
 );
 $version = "3.x-dev";

src/language.php

@@ -0,0 +1,6 @@
+<?php
+register_hook('options_save', function ($options) {
+  if (array_key_exists('ui_lang', $options)) {
+    $_SESSION['ui_lang'] = $options['ui_lang'];
+  }
+});