Document a breaking change in the default configuration

[roycaihw]

xref: #1284, OpenAPITools/openapi-generator#4485, OpenAPITools/openapi-generator#5315

Document a breaking change of kubernetes.config.Configuration() that exists since v12.0.0a1. Add a unit test that asserts the behavior.

Special notes:

1. The upstream change fixed a bug in different configuration objects unexpectedly sharing a common dict, but it broke the use case where people use Configuration() to easily access one global configuration.
2. Not sure if the test folder gets wiped when we regenerate the client. If so, we may need to carry a patch, or find another place to host it.
3. I looked at python-base and found the only place we use Configuration() is _refresh_oidc. The client doesn't rely on the default configuration.

[yliaog]

it's a bit confusing ...

kubernetes.config.Configuration() still returns the default "initial" configuration,
kubernetes.config.Configuration.get_default_copy() will return the default configuration if there is a default set via Configuration.set_default(c), otherwise, it will also return the default "initial" configuration

[roycaihw]

Updated. I reworded it a little bit, since the change in kubernetes.config.Configuration() was the regression.

[yliaog]

/lgtm
/approve

[palnabarun]

I was wondering if we should do this as a minor release since changelog and releases are usually immutable.

/hold
(just for resolving the above doubt, the change looks good to me 👍🏽)

[roycaihw]

@palnabarun Yes, I think that will help raise awareness. Would you mind fold the change to #1285, and add an action required note in 12.0.1?

[palnabarun]

Yeah sure. Let me cherry-pick your commit and apply there.

[palnabarun]

@roycaihw Can you please split your changes to the CHANGELOG and tests into two commits? I want to preserve attribution when I edit those. :)

[palnabarun]

The test addition also requires adding a note to the Hot Patch section to the release docs.

We need to specify that the commit which adds the test needs to be cherrypicked while performing the release.

[k8s-ci-robot]

New changes are detected. LGTM label has been removed.

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: roycaihw, yliaog

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[roycaihw]

@palnabarun Thanks. I split the commit into two

[palnabarun]

@roycaihw -- I have cherry picked both changes to the Release 12.0.1 PR. #1285

[roycaihw]

/close

in favor of #1285

[k8s-ci-robot]

@roycaihw: Closed this PR.

In response to this:

/close

in favor of #1285

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