Fix IDN domain name not being allowed

The filter_var function is unfortunately not perfect and doesn't support
domain with unicode as well as url with underscores. Replace usage with
a regex from Symfony validator.

See https://bugs.php.net/search.php?cmd=display&search_for=FILTER_VALIDATE_URL



Closes #27906

Signed-off-by: Carl Schwan <carl@carlschwan.eu>