Notify use-case admins of pending access requests

[Daniel-VM]

Access request notification workflow:

1. A public user submits a new AccessRequest.

2. pathocore-api stores the request with status=pending.

3. Instead of notifying only a static email list, pathocore-api queries Keycloak.

4. The API resolves enabled users with email addresses from the matching use-case admin group:

   /use-cases/<use_case>/admin

   Example for MEPRAM:

   /use-cases/mepram/admin

5. Those use-case admins receive the “new pending access request” email.

6. PATHOCORE_ACCESS_REQUEST_ADMIN_EMAILS remains available as fallback/general-copy recipients.

Summary

• Notify enabled Keycloak users in the matching use-case admin group when a new access request is created.
• Keep PATHOCORE_ACCESS_REQUEST_ADMIN_EMAILS as fallback/general-copy recipients if Keycloak lookup fails or extra admins should be notified.
• Add tests for Keycloak-derived recipients and fallback behavior.

Notes

Admin notification recipients are resolved from groups such as /use-cases/mepram/admin. Duplicate emails are removed before sending.

Validation

• python3 -m compileall -q core conf
• git diff --check
• python manage.py test core.tests.AccessRequestWorkflowTests