[Kestrel] Support for custom decoder for parsing target (e.g. URL)

[halter73]

Follow up to #17400. The idea is to make the encoding Kestrel interprets the target as configurable. Currently, Kestrel only accepts ASCII targets. This could be done with something like a "TargetEncoding" Encoding property on KestrelServerOptions.

[halter73]

@lodejard How important is it for you to be able to configure the encoding Kestrel uses to decode request targets?

[blowdart]

Of course we'd leave the default as the properly spec compliant one, won't we?

[halter73]

Of course we'd leave the default as the properly spec compliant one, won't we?

This issue is not about changing the default encoding, just making configurable. #17402 is about whether we should switch the default encoding from ASCII to UTF-8.

[ghost]

We've moved this issue to the Backlog milestone. This means that it is not going to be worked on for the coming release. We will reassess the backlog following the current release and consider this item at that time. To learn more about our issue management process and to have better expectation regarding different types of issues you can read our Triage Process.