Support Relative URLs not anchored at the root about akka-http

[johanandren]

I think this is the first time we have seen any requests to support such root-relative link headers (the only thing related I can find is a previous issue by you #99 ). Not anything we will prioritize but we'd be open to looking at PRs allowing such. Gut feeling is that it seems tricky to do in a binary compatible way.

[bblfish]

A workaround is to use RawHeader in this case.

RawHeader("Link","<../.acl>; rel=\"https://www.w3.org/ns/auth/acl#accessControl\"")

But given the close mapping between URLs and akka paths really a future version should perhaps take relative urls more seriously.

But that makes me wonder what happens if an Akka http client parses such a Link header... It should relativise the URLs to the base, but akka Uri does not have a method to do that.

[bblfish]

Speaking of the Link relation it seems to me that there it is a bit wasteful in cpu to calculate if the LinkValue relation contains the characters " ,;" before quoting one could always quote, especially when given a Uri. I think a better model for LinkParam in Scala3 would be LinkParam(key: String|Ur)I, then for Uri one could automatically add the quotes.

This has led me to discover a bug in http4s which assumed the quoting.