LDAP protocol/host/port configuration by URL; make BASE_DN optional

PHP ldap_connect($host, $port) function signature is deprecated: https://www.php.net/manual/en/function.ldap-connect.php

Querying an AD Global Catalog across an entire forest requires an empty base DN

app/Core/Ldap/User.php

@@ -342,10 +342,6 @@ class User
      */
     public function getBaseDn()
     {
-        if (! LDAP_USER_BASE_DN) {
-            throw new LogicException('LDAP user base DN empty, check the parameter LDAP_USER_BASE_DN');
-        }
-
         return LDAP_USER_BASE_DN;
     }