AAI-304 user details endpoint to combine Auth0 and backend user data

[marius-mather]

Description

AAI-304: want to get both Auth0 data and data from our database to display on individual user details pages.

Changes

• New endpoint to give combined user details
• Refactor to make some data schemas easier to use without circular imports
• Unit test for new endpoint

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