Preserve case of reason phrase from the actual server response

[andersjaensson]

Description

Some servers respond with an upper case reason phrase.

logbook-httpclient5 uses fixed reason phrase strings from org.zalando.logbook.HttpResponse.
This PR makes it take the reason phrase from the actual server response instead.

Example:

A request to https://httpbin.org/status/400

$ curl --head httpbin.org/status/400
HTTP/1.1 400 BAD REQUEST

will currently be logged like this by logbook:

HTTP/1.1 400 Bad Request

This change will make it log like this instead:

HTTP/1.1 400 BAD REQUEST

I guess this can possibly be considered a breaking change.

Motivation and Context

I want the log to be as close to the actual server response as possible.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.

[whiskeysierra]

@andersjaensson Can you rebase onto master to trigger a fresh build? The pipeline didn't run for some reason...

[whiskeysierra]

👍