HTTPCLIENT-2356: Extend Auth API and authentication Logic to enable m…

[ok2c]

…utual authentication

[ok2c]

@stoty Your changes are mostly intact. I folded AuthScheme2 into AuthScheme and changed some javadocs. Please review and approve.

[stoty]

Thank you @ok2c .

Using a default method instead of a new interface is a definite improvement over my version.

Two small issues:

1. This is only half of the solution for HTTPCLIENT-1625, I think it would be better to use
   HTTPCLIENT-2356 in the commit message.
   (I have not updated the commit message on my original PR to preserve continuity while reviewing, but was planning to)

2. This has my original mix of "authorization"/"authentication" log messages, you may want do a pass on those.

[stoty]

I was also planning to revert the disabled API check maven plugin before commit.

[ok2c]

@stoty Commit message and log statements have been corrected. Please do another pass.

[stoty]

+1 LGTM

[ok2c]

I am going to merge the PR later today unless someone objects. @michael-o Please do a post-commit review. If you see anything wrong with the change-set I will revert it.

[michael-o]

Will review this night

[ok2c]

@michael-o Corrected. Please do another pass.

[michael-o]

No objections

[arturobernalg]

LGTM