[BUG][C] Zero as integer in model

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

I have a yaml file in swagger: "2.0" format that includes integer that can be zero (see below). If I set the resolution or the framerate to zero, to indicate the first options, this will result in the argument not being sent. The following check is added inside the stream.c file:

// stream->resolution
if(stream->resolution) {
    if(cJSON_AddNumberToObject(item, "resolution", stream->resolution) == NULL) {
      goto fail; //Numeric
    }
}

If the resolution is set to zero, then if(stream->resolution) will return false and the zero is not added to the output.

openapi-generator version

openapitools/openapi-generator-cli@sha256:d2fee993745f8e003dfc5b79bbe03ae35a4a455540b084681c9a05deb601f7b0

OpenAPI declaration file content or url

 stream:
    type: "object"
    properties:
      resolution:
        type: "integer"
        format: "uint8"
        description: "Resolution
          0: 1920x1080\n
          1: 1280x720\n
          2: 960x544\n
          3: 800x600\n
          4: 800x480\n
          5: 704x400\n
          6: 640x480\n
          7: 640x360\n
          8: 320x240"
        minimum: 0
        maximum: 7
      framerate:
        type: "integer"
        format: "uint8"
        description: "Framerate.
          0: 60 FPS\n
          1: 50 FPS\n
          2: 10 FPS\n
        minimum: 0
        maximum: 2

Generation Details

Steps to reproduce

docker run --rm -v ${PWD}:/local openapitools/openapi-generator-cli:latest generate -i /local/restapi.yaml -g c -o /local/out/c

Related issues/PRs

Suggest a fix

I think something this line is fishy for integers.
https://github.com/OpenAPITools/openapi-generator/blob/04ebe9e1a0a9d51c04999659f3bdd169b7296a72/modules/openapi-generator/src/main/resources/C-libcurl/model-body.mustache#L347

Inspect modules/openapi-generator/src/main/resources/C-libcurl/model-body.mustache at the linked line, then reproduce with the provided Docker generation command and the YAML example. Verify the generated stream.c behavior for resolution or framerate set to zero; done means zero-valued integer arguments are included in the generated output.