libutil: Use Boost.URL for URI parsing

[xokdvium]

Motivation

Boost.URL is a significantly more RFC-compliant parser
than what libutil currently has a bundle of incomprehensible
regexes.

One aspect of this change is that RFC4007 ZoneId IPv6 literals
are represented in URIs according to RFC6874 1.

Previously they were represented naively like so: [fe80::818c:da4d:8975:415c\%enp0s25].
This is not entirely correct, because the percent itself has to be pct-encoded:

"%" is always treated as
an escape character in a URI, so, according to the established URI
syntax [RFC3986] any occurrences of literal "%" symbols in a URI MUST
be percent-encoded and represented in the form "%25". Thus, the
scoped address fe80::a%en1 would appear in a URI as
http://[fe80::a%25en1].

Context

Starting to pay off the tech debt #9603.
Fixes #10898.

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[Ericson2314]

I like this a lot!

But going to leave for others to review a bit just case there is some issues e.g. with how much Boost or compat I didn't think of

[Mic92]

Fixed some issue in to_string(), let me know what you think.

[xokdvium]

Ran the whole flake-regressions suite and hydraJobs.tests. Best I can tell this doesn't regress anything. What's great is that this also fixed a long-standing issue #10898.

[grahamc]

One concern I have is the flake regression suite only tests public flakes, and I suspect some flakes out there will no longer work correctly with new parsing semantics.

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On Sat, Jul 19, 2025, at 4:52 PM, Sergei Zimmerman wrote: *xokdvium* left a comment (NixOS/nix#13445) <#13445 (comment)> Ran the whole `flake-regressions` suite and `hydraJobs.tests`. Best I can tell this doesn't regress anything. What's great is that this also fixed a long-standing issue #10898 <#10898>. — Reply to this email directly, view it on GitHub <#13445 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAASXLH67Q2DEPSFXGBVUSL3JKVYVAVCNFSM6AAAAACBHRJBRKVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZTAOJSGU3DKNJWG4>. You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

[xokdvium]

I suspect some flakes out there will no longer work correctly with new parsing semantics.

I did see that Determinate runs GHA CI with a private flake-regressions-data repository.

work correctly with new parsing semantics.

Any particular issues you can think of? Did some of the prior non-compliance get ossified into lock files?
The several major deviations are 1) non pct-encoded spaces (which are handled explicitly in this patchset) and 2) the nested store URI queries, but this is also seemingly handled and tested.