[BUG] File upload Qt5cpp formdata

Description

Wrong headers in POST request due to "IsFormData" not set in generated OAIHttpRequest.cpp

openapi-generator version

3.3.4

OpenAPI declaration file content or url

post:
      description: Upload a file
      operationId: uploadFile
      consumes:
        - multipart/form-data
      parameters:
        - name: device_id
          in: path
          description: device serial number
          required: true
          type: string
        - name: resource_name
          in: path
          description: Filename
          required: true
          type: string
        - name: uploaded_file
          in: formData
          description: Uploaded file
          required: true
          type: file

Command line used for generation

java -jar openapi-generator-cli.jar generate -i pilot/api.yaml -g cpp-qt5 -o test

Suggest a fix

Not sure about the generator fix, but if you stumple across this issue, it can be fixed by setting the isFormData to true when it sets the layout.

if (input->files.length() > 0) { isFormData = true; input->var_layout = MULTIPART; }

Reproduce the issue with the supplied OpenAPI declaration and cpp-qt5 generation command, then inspect the generated OAIHttpRequest.cpp around multipart layout handling. Done means a file upload request sets IsFormData and produces the correct POST headers for multipart/form-data.