[BUG][KOTLIN][CLIENT] Unable to use `library` as additional properties

Created by: anantadwi13

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?
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Description

If we look at the documentation, kotlin client generator has a library config option. But we can't use it as additional properties.

openapi-generator generate -i specification.yaml -g kotlin -o output -p library=jvm-retrofit2

From the command above, it should generate kotlin client codes with retrofit2 as the HTTP client. But it used okhttp3 instead.

It will work as expected by passing library as parameter options.

openapi-generator generate -i specification.yaml -g kotlin -o output --library jvm-retrofit2

openapi-generator version

openapi-generator v5.3.1

Steps to reproduce

• Generate codes from specification.yaml

  openapi-generator generate -i specification.yaml -g kotlin -o output -p library=jvm-retrofit2