AAI-302 update registration code to create database records

[marius-mather]

Description

AAI-302: registration endpoints should now create user records in the backend database alongside registering the user in Auth0.

Changes

• Add user record creation in registration endpoints - BPA DP and Galaxy only, since these are the existing registration endpoints.
• Test user record creation
• Some improvements to our test setup to ensure we always run against the test database
• Other improvements to test setup/fixtures

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

[Copilot]

Pull Request Overview

This PR implements database record creation during user registration for BPA Data Portal and Galaxy platforms, fulfilling requirement AAI-302. The changes extend the existing Auth0-only registration to also create user records in the backend database.

• Add user record creation in registration endpoints for BPA DP and Galaxy
• Enhance test infrastructure to ensure consistent test database usage
• Update tests to verify database record creation alongside Auth0 registration

Reviewed Changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
routers/galaxy_register.py	Adds database user creation with Galaxy platform membership
routers/bpa_register.py	Adds database user creation with BPA platform membership
db/models.py	Adds helper methods for creating users from Auth0 data and platform memberships
auth0/client.py	Adds create_user method to Auth0Client
db/setup.py	Refactors database engine initialization to be lazy-loaded
tests/*.py	Updates tests to use new mocked Auth0 client and verify database operations
tests/conftest.py	Improves test infrastructure with better database isolation

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[amandazhuyilan]

One additional unit test requested.