HOFF-369: replace request with axios

[Rhodine-orleans-lindsay]

What?

Replace request module api with axios

Why?

Request module is deprecated and showing critical vulnerabilities in snyk scans so is being replaced with axios

How?

Replace the request module dependency with axios

• update model/index.js file and all related unit tests to work with axios. refactored to use async/await
• update model/apis/html-to-pdf-converter.js file and related unit tests to work with axios
• add model/apis/axiosSettings file to enable compatibility with axios and potential config changes
• update yarn.lock
• update Changelog

  Testing

  tests passing locally and tested in services locally and on branch

  Screenshots?(optional)

  Anything else?(optional)

  I have squashed Savant's commits into one (See his pr here https://github.com/UKHomeOfficeForms/hof/pull/400/files) and added mine after for clarity