Fix GHSA-w8qr-v226-r27w

We should not early-out with success status if we found an ipv6
hostname, we should keep checking the rest of the conditions.
Because integrating the if-check

Fix GHSA-w8qr-v226-r27w

We should not early-out with success status if we found an ipv6
hostname, we should keep checking the rest of the conditions.
Because integrating the if-check of the ipv6 hostname in the
"Validate domain" if-check made the code hard to read, I extracted the
condition out to a separate function. This also required to make
a few pointers const in order to have some clean code.

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