[Kotlin][okhttp] replace okhttpclient with callfactory

[vicmosin]

The issue with the generated open-api kotlin client is that is basically hardcodes an actual implementation of the client, by definition its type i.e. OkHttpClient, though many other extensions use Call.Factory interface to make it more extension-friendly and generic. For example, this observability interceptor.

The change is also should not be breaking change as the OkHttpClient type is actually an implementation of an Call.Factory interface. But tbh I am not sure as here the folks treated it as breaking change and introduced a new attribute to be able to extend the client properly.

PR checklist

• [ x] Read the contribution guidelines.
• [ x] Pull Request title clearly describes the work in the pull request and Pull Request description provides details about how to validate the work. Missing information here may result in delayed response from the community.
• [x ] Run the following to build the project and update samples:

  ./mvnw clean package 
  ./bin/generate-samples.sh ./bin/configs/*.yaml
  ./bin/utils/export_docs_generators.sh
  

  (For Windows users, please run the script in Git BASH)
  Commit all changed files.
  This is important, as CI jobs will verify all generator outputs of your HEAD commit as it would merge with master.
  These must match the expectations made by your contribution.
  You may regenerate an individual generator by passing the relevant config(s) as an argument to the script, for example ./bin/generate-samples.sh bin/configs/java*.
  IMPORTANT: Do NOT purge/delete any folders/files (e.g. tests) when regenerating the samples as manually written tests may be removed.
• [ x] File the PR against the correct branch: master (upcoming 7.6.0 minor release - breaking changes with fallbacks), 8.0.x (breaking changes without fallbacks)
• [ x] If your PR is targeting a particular programming language, @mention the technical committee members, so they are more likely to review the pull request.

@dr4ke616 (2018/08) @karismann (2019/03) @Zomzog (2019/04) @andrewemery (2019/10) @4brunu (2019/11) @yutaka0m (2020/03) @stefankoppier (2022/06)

[vicmosin]

@4brunu thnx, any estimates when we can get this released?

[4brunu]

Yes, you can find in the readme the planned releases.

https://github.com/OpenAPITools/openapi-generator#table-of-contents

If you need a new release earlier you can also build the jar from source and use it directly

https://github.com/OpenAPITools/openapi-generator?tab=readme-ov-file#table-of-contents