[BUG][cpp-restsdk] Generated code does not work

Created by: DominikPf

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• [4.0.2] What's the version of OpenAPI Generator used?
• Have you search for related issues/PRs?

Description

Version: 4.0.2 Docker

The Code Generator creates invalid Code for Model Definitions (Simple Interaction (string<->string seems fine)

OpenAPI declaration file content or url

swagger.zip

Steps to reproduce

1. Place swagger.json in the working directory
2. Execute Swagger Generator CLI via Docker

docker run --rm -v ${PWD}:/local openapitools/openapi-generator-cli:v4.0.2 generate -i local/swagger.json -g cpp-restsdk -o /local/TestApi.Client/

3. Try to compile c++ Code Multiple errors in TestEntity & TestEntityApi

But Code seems fine for this line: https://github.com/OpenAPITools/openapi-generator/blob/fae9d4a37be74347abbe1cb3dd5b795d198c54de/modules/openapi-generator/src/main/resources/cpp-rest-sdk-client/model-source.mustache#L28

Is the cpp-restsdk generator not in the current Version? (Git Tag is also used)