force 2fa for group of users (#456)

Authored-by: Antonio Cordeddu <coranto@yetopen.com>

tests/_fixtures/data/auth_assignment.php

@@ -0,0 +1,8 @@
+<?php
+
+return [
+    'auth_assignment' => [
+        'item_name' => 'admin',
+        'user_id' => '1',
+    ],
+];