[BUG] Incorrect code is generated in typescript-fetch generator for oneOf construct

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

1. Generated models contains incorrect import statements like

import {
    ActionRequestStepDto | ActivityRequestStepDto | DownloadConfirmationRequestDto | LinkConfirmationRequestDto,
    ActionRequestStepDto | ActivityRequestStepDto | DownloadConfirmationRequestDto | LinkConfirmationRequestDtoFromJSON,
    ActionRequestStepDto | ActivityRequestStepDto | DownloadConfirmationRequestDto | LinkConfirmationRequestDtoFromJSONTyped,
    ActionRequestStepDto | ActivityRequestStepDto | DownloadConfirmationRequestDto | LinkConfirmationRequestDtoToJSON,
} from './ActionRequestStepDto | ActivityRequestStepDto | DownloadConfirmationRequestDto | LinkConfirmationRequestDto';

2. XXToJSON converter's maps are also wrong

'steps': ((value.steps as Array<any>).map(ActionRequestStepDto | ActivityRequestStepDto | DownloadConfirmationRequestDto | LinkConfirmationRequestDtoToJSON)),

3. Inherited models contain duplicated imports

import {
    AbstractRequestStepDto,
    AbstractRequestStepDtoFromJSON,
    AbstractRequestStepDtoFromJSONTyped,
    AbstractRequestStepDtoToJSON,
} from './AbstractRequestStepDto';
import {
    ActionRequestStepDto,
    ActionRequestStepDtoFromJSON,
    ActionRequestStepDtoFromJSONTyped,
    ActionRequestStepDtoToJSON,
} from './ActionRequestStepDto';
import {
    ActionRequestStepDtoAllOf,
    ActionRequestStepDtoAllOfFromJSON,
    ActionRequestStepDtoAllOfFromJSONTyped,
    ActionRequestStepDtoAllOfToJSON,
} from './ActionRequestStepDtoAllOf';
import {
    ActivityRequestStepDto,
    ActivityRequestStepDtoFromJSON,
    ActivityRequestStepDtoFromJSONTyped,
    ActivityRequestStepDtoToJSON,
} from './ActivityRequestStepDto';
import {
    DownloadConfirmationRequestDto,
    DownloadConfirmationRequestDtoFromJSON,
    DownloadConfirmationRequestDtoFromJSONTyped,
    DownloadConfirmationRequestDtoToJSON,
} from './DownloadConfirmationRequestDto';
import {
    LinkConfirmationRequestDto,
    LinkConfirmationRequestDtoFromJSON,
    LinkConfirmationRequestDtoFromJSONTyped,
    LinkConfirmationRequestDtoToJSON,
} from './LinkConfirmationRequestDto';

import {
     ActionRequestStepDtoFromJSONTyped,
     ActivityRequestStepDtoFromJSONTyped,
     DownloadConfirmationRequestDtoFromJSONTyped,
     LinkConfirmationRequestDtoFromJSONTyped
} from './';
 herer ^^^^^^^^^^^^^

4. Generated model have circular references to it's own definition

export interface ActionRequestStepDto extends AbstractRequestStepDto {

export type AbstractRequestStepDto =
  | ({ stepType: "ACTION" } & ActionRequestStepDto)
  | ({ stepType: "ACTIVITY" } & ActivityRequestStepDto)
  | ({ stepType: "ActionRequestStepDto" } & ActionRequestStepDto)
  | ({ stepType: "ActivityRequestStepDto" } & ActivityRequestStepDto)
  | ({ stepType: "DOWNLOAD_CONFIRMATION" } & DownloadConfirmationRequestDto)
  | ({
      stepType: "DownloadConfirmationRequestDto";
    } & DownloadConfirmationRequestDto)
  | ({ stepType: "LINK_CONFIRMATION" } & LinkConfirmationRequestDto)
  | ({ stepType: "LinkConfirmationRequestDto" } & LinkConfirmationRequestDto);

Validator respose

This API is valid, but it cannot be shown because it contains circular references

toText@https://apitools.dev/swagger-parser/online/js/bundle.min.js:17:226677

openapi-generator version

5.4.0

OpenAPI declaration file content or url

https://gist.github.com/Dema/01985a4a8f78040adcdf02b7d5cb8d76

Generation Details

java -jar openapi-generator-cli generate -g typescript-fetch --additional-properties=typescriptThreePlus=true,enumPropertyNaming=original,supportsES6=true,legacyDiscriminatorBehavior=false,useOneOfInterfaces=true

Steps to reproduce

Related issues/PRs

Suggest a fix

Start with the OpenAPI declaration at the linked gist and run the provided openapi-generator-cli typescript-fetch command with its additional properties. Compare the generated imports, ToJSON mappings, inherited-model imports, and oneOf types with the reported output; done means these generated models no longer contain invalid or duplicated references.