OTP : 2FA Authentication

Improve : tighten the security + cosmetic
set double authentication : create, send link, usable with Google Authenticator and FreeOTP

1. OTP : prevent direct access without going throught the 2FA mechanism
2. Go back to the url where you were disconnected
3. Cosmetic

html/index.php

@@ -211,11 +211,21 @@ if (strlen(domaine)>0)
 {
     $my_domain=sprintf(_("Domaine")." : %s", domaine);
 }
-
+/**
+ * if request to recover password
+ */
 if (defined("RECOVER")&&isset($_REQUEST['recover']))
 {
     require_once '../include/recover.php';
 }
+/*
+ * if request to see OTP qrcode
+ */
+if ( isset($_GET['otp'])){
+    
+    require_once '../include/otp-link.php';
+    return;
+}
 // reconnect , create a variable to reconnect properly in login.php
 $goto="";
 if (isset($_REQUEST['reconnect'])&&isset($_REQUEST['backurl']))