[BUG][scala-http-client] Default body should not be a single space

[mickaelmagniez]

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

The default body sent (for example POST request without any body) is " " (single space character).

Some backends (for example akka-http) failed to parse it as json.

So it will be better so send an empty body rather than just a space.

openapi-generator version

5.2.1

OpenAPI declaration file content or url

Generation Details

Steps to reproduce

Related issues/PRs

Suggest a fix

[chameleon82]

Is that behavior related to scenario when client send header Content-Type: application/json ?

I that case it make sense to not send that header as well as there is no content.