[BUG] [typescript-angular] blob request return type is never string, but always generated as string

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

When generating a request that returns blobs, the generated method is defined to return strings.
However, if you look at the implementation, it actually returns:

• text if acceptHeader is text
• an object if the acceptHeader is JSON
• a Blob if the acceptHeader is anything else.

None of these are string, so its always wrong.

openapi-generator version

6.3.0, not a regression

OpenAPI declaration file content or url

{
  "openapi" : "3.0.1",
  "info" : {"title" : "Issue sample", "version" : "1"},
  "paths" : {
    "/proof" : {
      "get" : {
        "operationId" : "getProof",
        "responses" : {
          "default" : {
            "description" : "The blob output stream",
            "content" : {
              "application/octet-stream" : {
                "schema" : {
                  "type" : "string",
                  "format" : "byte"
                }}}}}}}}
}

Generation Details

language: typescript-angular

Steps to reproduce

Generate the project, see api/default.service.ts.

Use the provided OpenAPI declaration with the typescript-angular generator, then inspect api/default.service.ts and compare the declared return type with the implementation's text, JSON, and Blob branches. Done means the generated method's type accurately represents the documented runtime outcomes for the supplied example.