[BUG][Security][Javascript][Typescript] NPM high severity vulnerabilities while running UTs

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

As part of running the unit tests for #4672, I saw the following message in the UT logs, and I am opening this issue to track the security vulnerability.

found 33 high severity vulnerabilities
run npm audit fix to fix them, or npm audit for details

It looks like openapitools is using a version of npm that has high vulnerabilities.

openapi-generator version

It was master on December 2, 2019.

OpenAPI declaration file content or url

The problem is reproducible out-of-the-box with the OAS files that are included in the OpenAPITool repo. It is a build tool chain issue.

Command line used for generation

Steps to reproduce

Related issues/PRs

Suggest a fix

Start by reproducing the unit-test dependency audit using the OpenAPI Generator repository's included OAS files and inspect the output of npm audit. Trace the build tool chain and its JavaScript/TypeScript dependencies, then verify that the reported high-severity vulnerabilities are resolved without breaking the unit tests.