Make UAA token copyable from frontend

[bmo-at-a9s]

This change enables users to copy the uaa bearer token used for cloudfoundry auth straight from the frontend, e.g. to use in the cf cli for testing purposes.

How Has This Been Tested?

There are unit tests that have been added both for the frontend part of this functionality as well as the backend.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• Docs update
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have followed the guidelines in CONTRIBUTING.md, including the required formatting of the commit message