Surface Warning header

[cben]

Since 1.19, apiserver may set Warning: header on responses. https://kubernetes.io/blog/2020/09/03/warnings/

How may we expose it to callers?
NOT an exception, this is for stuff like deprecated APIs that however should still work.
The common use case is probably to log them, but should be customizable.
So, add a param to Client.new() specifying a callback / logger object?

[andrzej-stencel]

Yes I agree, being able to log the warning to a user-provided logger instance sounds like a good idea.