AAI-268 Get or create the Auth0 role before adding it to the DB

[marius-mather]

Description

AAI-268: allow for roles already existing when calling the API to add them to the database

Changes

• Check for existing Auth0 role and only create it if needed
• Unit tests

Checklist

• I have commented my code, particularly in hard-to-understand areas
• I have added unit / integration tests that prove my fix is effective or that my feature works
• I have run all tests locally and they pass
• I have updated the documentation (if applicable)

How to Test Manually (if necessary)

Run uv run pytest