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

tests/units/Core/Ldap/LdapUserTest.php

@@ -785,14 +785,6 @@ class LdapUserTest extends Base
         $this->assertEquals(array('is_ldap_user' => 1), $user->getExtraAttributes());
     }
 
-    public function testGetBaseDnNotConfigured()
-    {
-        $this->expectException('\LogicException');
-
-        $user = new User($this->query);
-        $user->getBaseDn();
-    }
-
     public function testGetLdapUserPatternNotConfigured()
     {
         $this->expectException('\LogicException');