Let the PreemptiveHttpClient use the SPNEGO kerberos ticket on windows systems

[nilleb]

On windows systems, artifactory can be behind an apache frontend which acts as a reverse proxy, just filling the REMOTE_USER property in order to allow artifactory authorization. (This is configurable in the artifactory HTTP SSO onfiguration section).

In such a scenario Jenkins fails to publish, with a 401 error code.

Could you please provide an extension point to allow third party developers to access the PreemptiveAuth HttpRequestInterceptor, or (use the provided username/password as NTCredentials and get the current user SPNEGO kerberos ticket to authentify)?