Unix Domain Socket URLs are not idempotent

AHC has an interesting quirk with how it supports unix: URLs - if the URL has a baseURL, the path of that base URL is taken as the socket path, and the relative path on top is taken as the path "within" the socket.

Basically it's squishing 2 paths in to the same URL - but not the same URL string, just the URL object. It's just an extremely fragile artefact of Foundation's URL model, and is not idempotent with respect to serialization, the .absoluteURL property, or many of the other modifications people like to make to URLs.

In fact it's so fragile that I'd argue the only way to reliably use this feature is directly in the Request initializer. If that's the case, a new initializer on Request would fulfil that need better (of course, there are also http+unix: URLs if you need to encode the entire request as a URL, and they do not have any of these idempotence issues).

Would it be possible to deprecate and remove the UDS base-path quirk?

Offending code is here - note that the socket path and uri depend on the presence of a base URL.

Start in Sources/AsyncHTTPClient/HTTPHandler.swift around the linked code, where the socket path and URI depend on whether a base URL exists. Trace how Unix domain socket URLs behave through serialization and absoluteURL, then determine the deprecation/removal and Request-initializer changes needed. Done means the fragile base-path behavior is addressed without losing a reliable way to issue requests over Unix domain sockets.