In order for uaa_jwt settings to be populated by config files, they have to be part of a defined and running application. This PR adds support for a uaa_jwt sub-key of the main rabbitmq_auth_backend_oauth2 env key.
"OAuth 2" is many things but it's still more descriptive, open-ended and easier
to find than "uaa" (too tool-specific) or "jwt" (too narrow, not known widely enough).
Per discussion with @hairyhum @kjnilsson.
Luke Bakken
Michael Klishin
Michael Klishin