Store status code in exception for ProxyTunnelError

[stephentoub]

Fixes #105546
Closes #66329

@antonfirsov, @wfurt, is it by-design or an accident that we didn't do this? The original PR:
https://github.com/dotnet/runtime/pull/88974/files#diff-bc2faad6c76ecb9b115e305763eb55ebfde74de1eee27ed549e5edaabb097a99R1767
has it with the status code only going into the error message but not being used to intialize the property.

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[wfurt]

LGTM.
I don't know if this was the reason but at some point there was concern about mingling status from proxy vs actual server. #48679

It seems like this effectively solves #66329, right? e.g. the ask is the same.

[stephentoub]

It seems like this effectively solves #66329, right? e.g. the ask is the same.

I believe so

I don't know if this was the reason but at some point there was concern about mingling status from proxy vs actual server. #48679

I read through that and it doesn't actually seem like being about status, rather than the response couldn't be differentiated from the actual response, and the resulting fix was to throw this exception. Now that an exception is being thrown and that exception can carry a status code, providing that status code seems like the correct answer. It's clear it's a proxy tunnel failure from the error enum.

[wfurt]

that make sen se to me. Can we add test(s) and perhaps also update documentation to make it clear?

[antonfirsov]

@antonfirsov, @wfurt, is it by-design or an accident that we didn't do this?

HttpRequestException.StatusCode has been introduced in #32455 but hasn't been systematically forwarded for cases other than trivial EnsureSuccessStatusCode() validations. #88974 didn't change anything in that regard.

[stephentoub]

but hasn't been systematically forwarded for cases

Meaning we're likely missing the status code being included in the exception in other cases? Is there an open issue for auditing all of them?

[antonfirsov]

Opened #105700.