[BUG]`typescript-axios` generator does not respect `useSingleRequestParameter` option, defaulting to true in all cases

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 am using the typescript-axios generator, and I am observing it not respect the useSingleRequestParameter option.

It is always set to true, which is odd because it is supposed to default to false. I am using the standard PetStore example schema, and have provided a minimal repo as repro.

openapi-generator version

v6.6.0 of the generator CLI

OpenAPI declaration file content or url

Here is a repo with instructions to reproduce. https://github.com/jonchurch/openapi-generator-issues

Generation Details

The schema is the PetStore example (although the schema does not matter, using it for simplicity here).

I am using the @openapi-tools/openapi-generator-cli package

All config is kept in openapitools.json the value of which is:

{
  "$schema": "./node_modules/@openapitools/openapi-generator-cli/config.schema.json",
  "spaces": 2,
  "generator-cli": {
    "version": "6.6.0",
    "generators": {
      "v2.0" : {
        "generatorName": "typescript-axios",
        "output": "./test",
        "inputSpec": "https://raw.githubusercontent.com/OpenAPITools/openapi-generator/master/modules/openapi-generator/src/test/resources/3_0/typescript-axios/with-separate-models-and-api-inheritance.yaml",
        "additional-properties": {
          "useSingleRequestParameter": true,
          "withSeparateModelsAndApi": true,
          "apiPackage": "api",
          "modelPackage": "models"
        }
      }
    }
  }
}

Steps to reproduce

All reproduce steps are in included in the repo.

But, all the repo is doing is running the generate command with the above openapitools.json configuration.

To repro:

1. Run the generate command in the repo, npm run generate
2. Then, disable useSingleRequestParameter by setting it to false or removing the option entirely.
3. Re-generate using npm run generate in the repo.
4. Observe that there is no diff, the generated code has not changed it's function signatures to reflect no longer using a single request parameter.

Related issues/PRs

Suggest a fix

Start by running the linked reproduction repository with its openapitools.json and the npm run generate command. Compare generated function signatures with useSingleRequestParameter set to true, false, and omitted; done means the generated output changes appropriately between those cases.