[Kotlin] Allow other content-types when only interested in status-code / Unit

[roelwuytens-androme]

This PR addresses a specific issue we noticed with the Kotlin generator when the API returns a content type other than JSON.

For example express JS will return "OK" with response-type text/plain

res.sendStatus(200)

This results in an exception when parsing the response body (see https://github.com/OpenAPITools/openapi-generator/blob/v7.8.0/samples/client/petstore/kotlin-nullable/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt#L188)
We're only interested in success/failure:

      responses:
        '200':
          description: Updated

To solve this we've added a check on Unit.

Technical Committee Kotlin:
@dr4ke616 @karismann @Zomzog @andrewemery @4brunu @yutaka0m @stefankoppier

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[4brunu]

Thanks for the PR 👍

[4brunu]

Thanks for the PR but your commit (as shown in the Commits tab) is not linked to your Github account, which means this PR won't count as your contribution in https://github.com/OpenAPITools/openapi-generator/graphs/contributors.

Let me know if you need help fixing it.

Ref: https://github.com/OpenAPITools/openapi-generator/wiki/FAQ#how-can-i-update-commits-that-are-not-linked-to-my-github-account

[roelwuytens-androme]

Thanks for the quick feedback!
I've updated my account, and the commits are now linked to my GitHub account, thanks for the link.

[4brunu]

Merged 👍 thanks for contributing to this project