RFR: 8326949: Authorization header is removed when a proxy Authenticator is set on HttpClient

[Michael McMahon]

On Sun, 29 Sep 2024 16:46:06 GMT, Michael McMahon <michaelm at openjdk.org> wrote:

> This fix relaxes the constraints on user set authentication headers. Currently, any user set authentication headers are filtered out, if the HttpClient has an Authenticator set. The reason being that the authenticator is expected to manage authentication.  With this fix, it will be possible to use pre-emptive authentication through user set headers, even if an authenticator is set. The expected use case is where the authenticator would manage either proxy or server authentication and the user set headers would manage server authentication if the authenticator is managing proxy (or vice versa).
> If the pre-emptive authentication fails, then this behavior is disabled on further retries and it would be up to the authenticator to provide the right credentials then.
> 
> Thanks,
> Michael

Quite a few existing authentication regression tests are failing with the change. So, I need to investigate them and will address the other PR comments after that.

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PR Comment: https://git.openjdk.org/jdk/pull/21249#issuecomment-2383458627