Update openapi generator v4.2.3

[sheldonkwok]

I was interested in adding a keepalive agent to the kubernetes clients requests.
This PR adds an "interceptor" model to the request options and it's in openapi generator v4.2.3.

In this PR, I have updated settings for this new openapi generator. I also changed the kubernetes-client/gen commit to one that uses node v10 since v8 is deprecated.

I ran the gen locally and it completed successfully but didn't include that since I wasn't sure if there were any other steps required.

[sheldonkwok]

/assign @brendandburns

[brendandburns]

Please do run the gen locally and include that as a separate commit in this PR.

Thanks!

[sheldonkwok]

Okay, pushed. I noticed the kubernetes/api/openapi-spec/swagger.json is now unversioned so everything is tagged with the branch name instead of the actual version. Is that okay now?

[brendandburns]

Do you have any idea why the tag changed? is it because of a change in the openapi generator?

I'd like to understand why that changed, and then we can merge this.

Thanks!

[sheldonkwok]

Yeah in this commit the version was dropped from the openapi spec swagger.json
kubernetes/kubernetes@146d503#diff-9ce7ea8441086bf1902b4f936f4601d0

This seems to have been applied across multiple release branches. We were using branch release-1.15. In https://github.com/kubernetes-client/gen/blob/master/openapi/preprocess_spec.py#L379, unversioned specs end up taking on the branch/tag name so it became release-1.15. I just regenerated using the latest 1.15 tag (1.15.10). So now the file headers look more consistent. It seems like we should use the tag over the branch moving forwards.

[brendandburns]

/lgtm
/approve

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