Steps to reproduce:
1. Add site factory config (https://doc.ibexa.co/en/latest/multisite/site_factory/site_factory/)
2. Add a new site (1st pic) (Domain has to contains special char /)
3. Add LP to the new site
4. In the added LP click on 'Preview' button

Actual result:
Error 500 occurs (2nd pic).

Expected result:
'Domain' field should have validation for special chars (.ie /).