This commit accept IPv6 nodes submission.
When user submit new public node, the server will check IP addresses
from given hostname. If host IP addresses doesn't have IPv4, it will
be recorded as "IPv6 only" node.
Probers that support IPv6 may add `IPV6_CAPABLE=true` to the `.env`
file.
Please note that this feature still experimental and may not being
merged to the main branch.
Only return with status code `1` if error type is `errProber` which one
of this following const:
errNoEndpoint, errNoTorSocks, errNoAPIKey, and errInvalidCredentials.
