[BUG] [java-micronaut-server] Binary file to download has a wrong object type

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?

Description

If the Micronaut endpoint returns a binary file, micronaut uses object types SystemFile or StreamedFile.
But the problem is, if the Openapi definition has format: binary, the generated endpoint returns object CompletedFileUpload. This object is uses to upload file using multipart, but not to download the file.

openapi-generator version

I use the latest version OpenAPI Generator with maven plugin v6.6.0.

OpenAPI declaration file content or url

/download:
  get:
    tags:
      - download
    description: Download file
    operationId: downloadFile
    responses:
      "200":
        description: Response with encrypted ZIP file includes all application log files
        content:
          application/octet-stream:
            schema:
              type: string
              format: binary

Generation Details

@Get(uri="/download")
@Produces(value = {"application/octet-stream"})
public HttpResponse<CompletedFileUpload> downloadFileApi() {
    return downloadFile();
}

Steps to reproduce

1. Create an endpoint with content type application/octet-stream and schema format binary.
2. Generate code with java-micronaut-server.
3. Check the generated controller.

Related issues/PRs

Related ticket to generate OpenAPI definition from the implementation and swagger annotations - https://github.com/micronaut-projects/micronaut-openapi/issues/441

Start by tracing the java-micronaut-server generator's handling of an OpenAPI response with type string and format binary, then inspect the generated downloadFileApi controller shown in the report. Done means binary downloads return a Micronaut download type such as SystemFile or StreamedFile rather than CompletedFileUpload; validate by regenerating the provided endpoint.