[BUG] typescript-angular variables.ts should not be used if supportingFiles are disabled

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• What's the version of OpenAPI Generator used?
• Have you search for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Bounty to sponsor the fix (example)

Description

Running the generator with -D models,apis skips generating supportingFiles, but the generated service uses the missing variables.ts (part of supportingFiles).

openapi-generator version

4.1.3

OpenAPI declaration file content or url

openapi: 3.0.0
info:
  title: Deployed APIs
  version: 1.0.0
servers:
- url: http://localhost:8181
- url: https://localhost:8543
paths:
  /api/hello/{name}:
    get:
      description: Say hello to someone
      operationId: sayHello
      parameters:
      - name: name
        in: path
        description: name
        required: true
        schema:
          type: string
      responses:
        200:
          description: Ok
          content:
            '*/*':
              schema:
                $ref: '#/components/schemas/HelloObject'
  /api/hello:
    get:
      description: Say hello world
      operationId: sayHelloWorld
      responses:
        200:
          description: Ok
components:
  schemas:
    HelloObject:
      type: object
      properties:
        message:
          type: string

Command line used for generation

openapi-generator generate -i http://localhost:8181/openapi/ -g typescript-angular -o src/lib/model -D models,apis --additional-properties='stringEnums=true,fileNaming=kebab-case'

Steps to reproduce

Run the generator with given command line and try to build the project.

excerpt of generated file:

import { BASE_PATH, COLLECTION_FORMATS }                     from '../variables';
import { Configuration }                                     from '../configuration';


@Injectable({
  providedIn: 'root'
})
export class DefaultService {

Suggest a fix

Merge the configuration and variables into one file or do not use them.

Inspect the typescript-angular generator's supportingFiles handling and the generated variables.ts and configuration imports; reproduce the issue with the shown command and OpenAPI example while disabling supportingFiles. Done when a models/apis-only generation no longer references missing supporting files and the generated project builds.