Pdcl 4946 Consume better JWT token exchange errors

[brenthosie]

Resolves #28

Description

jwt-auth is now providing a lot more useful information about why the token exchange fails. We can now observe that information and display it to the user.

Related Issue

https://jira.corp.adobe.com/browse/PDCL-4946

Motivation and Context

Users didn't understand in many scenarios why they were unable to get an access token.

How Has This Been Tested?

1. Manual test of uploader
2. npm test

Screenshots (if appropriate):

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [x] I have signed the Adobe Open Source CLA.
• [x] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [x] I have read the CONTRIBUTING document.
• [x] I have added tests to cover my changes.
• [x] All new and existing tests passed.

[brenthosie]

Relies on https://github.com/adobe/jwt-auth/pull/53