Adding proxy headers options for configurations.

[chowmean]

This PR addresses #735

Added options to pass proxy headers in Configuration objects and then pass it to proxy_manager in RESTClientObject.

[k8s-ci-robot]

Thanks for your pull request. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

📝 Please follow instructions at https://git.k8s.io/community/CLA.md#the-contributor-license-agreement to sign the CLA.

It may take a couple minutes for the CLA signature to be fully registered; after that, please reply here with a new comment and we'll verify. Thanks.

---

• If you've already signed a CLA, it's possible we don't have your GitHub username or you're using a different email address. Check your existing CLA data and verify that your email is set on your git commits.
• If you signed the CLA as a corporation, please sign in with your organization's credentials at https://identity.linuxfoundation.org/projects/cncf to be authorized.
• If you have done the above and are still having issues with the CLA being reported as unsigned, please email the CNCF helpdesk: helpdesk@rt.linuxfoundation.org

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository. I understand the commands that are listed here.

[yliaog]

/lgtm

[chowmean]

I signed it

[yliaog]

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

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

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [yliaog]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[tomplus]

I'm afraid these files are generated by swagger-codegen.

[chowmean]

I'm afraid these files are generated by swagger-codegen.

@tomplus created this in upstream. swagger-api/swagger-codegen#9278

[chowmean]

OpenAPITools/openapi-generator#2467 Added this in openapi-generators for your plan to migrate to open api generator

[tdevilleduc]

I cannot find this pull request merged in master branch
It seems this commit has erased the pull request code :
b603b4a#diff-fe9854b0d36c4421253521aa342e6276

[micw523]

The PR author changed a file in the automatically generated codes so that the change is overwritten in the next release. The Openapi generator PR is merged however so that the change should be carried on forward.