feat: send emails to sbp admins for new user registration

[amandazhuyilan]

Description

Currently when a new user registers for a SBP account, an email is sent to aai-dev@biocommons.org.au. This email should go to instead all SBP admins.

Changes

• Add Platform.get_admins, mirroring group admin lookup, to fetch platform admin emails from Auth0 roles.
• Update SBP registration flow to notify SBP admins instead of the hard-coded address.
• Extend tests for SBP registration and platform admin email collection to cover the new behavior.

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.

[marius-mather]

Looks good apart from the unnecessary migration

[marius-mather]

approved!

[amandazhuyilan]

This is the last pull request of 2025!