[BUG] [typescript-node] Query parameters do not support `explode: false, style: form`

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

CSV array serialization for query parameter is not supported for OAS3. It seems that explode is ignored at all.

openapi-generator version

5.0.1

OpenAPI declaration file content or url

Pet Store API OAS3 with modified listPets that accepts query parameter tags (explode: false, style: form)

        - name: tags
          in: query
          description: Filter by tags
          required: false
          allowEmptyValue: true
          style: form
          explode: false
          schema:
            type: array
            items:
              type: string

Generation Details

Command:

npx @openapitools/openapi-generator-cli generate \
  -i ./petstore.yaml \
  -g typescript-node --generate-alias-as-model \
  -c ./codegen.config.json \
  -o ./generated/

Contents of codegen.config.json:

{
  "sortParamsByRequiredFlag": true,
  "ensureUniqueParams": true,
  "allowUnicodeIdentifiers": false,
  "modelPropertyNaming": "camelCase",
  "supportsES6": false,
  "snapshot": false,
  "typescriptThreePlus": true
}

Steps to reproduce

1. Generate the code
2. Add a debugging console.log statement to petsApi.ts:L208: console.log(localVarRequest(localVarRequestOptions).uri.query)
3. Instantiate api and call the method

import { PetsApi } from './generated/api'

const api = new PetsApi()
api.listPets(10, ["dog", "cat"])

4. Output will be limit=10&tags%5B0%5D=dog&tags%5B1%5D=cat

Expected: limit=10&tags=dog,cat

Related issues/PRs

I think this issue is related: https://github.com/OpenAPITools/openapi-generator/issues/7973

Suggest a fix

Not able, but with few advices on which template variables to use and example implementation in other clients I might be able to fix it and send pull request.

Reproduce the issue with the provided Pet Store OAS3 declaration and typescript-node generation command. Start at generated petsApi.ts around line 208, then trace the typescript-node request query serialization to see how the tags array is encoded. Done means explode:false with style:form produces tags=dog,cat instead of indexed tags parameters, with coverage for the reported case.