[BUG] typescript-fetch with basic auth throws: ReferenceError: btoa is not defined

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?

Description

typescript-fetch with basic auth throws: ReferenceError: btoa is not defined

openapi-generator version

openapi-generator version
4.0.0-beta3

OpenAPI declaration file content or url

anything using basic auth

Command line used for generation

all

Steps to reproduce

1. generate with typescript-fetch and basic auth
2. use it inside nodejs project
3. call the API

Expected: works

Actual: ReferenceError: btoa is not defined

Still error even after npm install --save btoa

Related issues/PRs

Suggest a fix

Workaround:

npm i --save btoa
npm i --save-dev @types/btoa

add to each API:

import btoa from "btoa";

Start with the typescript-fetch generated client and reproduce the basic-auth request in a Node.js project, following the listed generation and call steps. Compare the failing btoa usage with the documented btoa package workaround; done means basic authentication works without a ReferenceError.