For the AO defined in the URL specification, in the case the
domain does not match against the PSL, we should be returning
the TLD. This fixes a crash for a bunch of WPT tests using the
Document.domain setter when the test is being served by WPT
locally.
We should be doing similar logic in registrable_domain, but that
unfortunately runs into some other issues, so just leave a FIXME
for now.
It is confusing to have both URL::Host::public_suffix and
URL:get_public_suffix, both with slightly different semantics.
Instead, use PublicSuffixData for cases that just want a direct
match against the list, and URL::Host::public_suffix in LibWeb
land as the URL spec defined AO.
We were using the public suffix of the URL's host as its registrable
domain. But the registrable domain is actually the public suffix plus
one additional label.
Specifically, after implementing some recent spec changes to navigables,
we end up calling `get_public_suffix("localhost")` here, which returns
OptionalNone. This would previously crash.
Our get_public_suffix() seems a little incorrect. From the spec:
> If no rules match, the prevailing rule is "*".
> https://github.com/publicsuffix/list/wiki/Format#algorithm
However, ours returns an empty Optional in that case. To avoid breaking
other users of it, this patch modifies Host's uses of it, rather than
the function itself.
This lets us move a few Host-related functions (like serialization and
checks for what the Host is) into Host instead of having them dotted
around the codebase.
For now, the interface is still very Variant-like, to avoid having to
change quite so much in one go.
