AAI-288 AAI-277 update username and password requirements, update registration data

[marius-mather]

Description

AAI-288 and AAI-277: updating username and password formats to match the requirements in the current BPA and Galaxy stories. We also now to submit username as a standard part of registration, rather than in user_metadata

Changes

• Create validated types for username and password to enforce their format
• Update registration data models to use username and password
• Remove username from user_metadata and submit it in the main registration data
• Unit tests for username and password formats

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