[minh-biocommons]

Description

Add an authenticated profile email availability endpoint so the front end can check whether an email is already in use before checking institutional eligibility through AAF

Changes

• Add GET /me/profile/email/check-availability for authenticated Auth0 and AAF users
• Share conflict checks across profile email updates, OTP confirmation, and AAF migrations

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)
• For any new secrets, I have updated the shared spreadsheet and the GitHub Secrets.

[Copilot]

🟢 Approval recommended

No active review issues are recorded for the authenticated profile email availability changes.

No open issues 🎉

What changed in this PR

Adds an authenticated profile email availability check for Auth0 and AAF users, allowing the frontend to detect conflicts before checking institutional eligibility.

Changes:

• Adds GET /me/profile/email/check-availability with a shared availability response schema.
• Centralizes case-insensitive conflict checks across profile updates, OTP confirmation, and AAF migrations, including deleted accounts while excluding the current user.
• Expands tests for authentication, validation, and emails claimed after an earlier availability check or OTP request.

File	Description
tests/​test_user.py	Tests availability checks and conflict handling during email changes.
tests/​test_aaf.py	Updates expected migration conflict messages.
services/​email_availability.py	Introduces shared email availability and conflict checks.
schemas/​responses.py	Defines the shared availability response schema.
routers/​utils.py	Reuses the shared schema for registration availability checks.
routers/​user.py	Adds the profile availability endpoint and adopts shared conflict checks.
routers/​aaf.py	Reuses the shared conflict helper and aligns error messages.

_{Review effort: Balanced}

[marius-mather]

looks great! thanks for the refactor