feat: enable unrevocation for users' access to services

[amandazhuyilan]

Description

AAI-523: Un-revoke users from services via reattaching the related Auth0 roles

Changes

• Platform approvals now load the Auth0 client dependency and reattach the platform role whenever a membership transitions back to approved, so an “unrevoke” via the approve endpoint restores Auth0 access
• Added PlatformMembership.grant_auth0_role so the role assignment mirrors the existing revoke helper and centralizes the Auth0 role naming logic
• Extended coverage to ensure the new helper behaves correctly and that the admin approval endpoint actually calls Auth0 to add the role

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.

How to Test Manually (if necessary)

All new and old unit tests shall pass in CI.

[marius-mather]

Looks good but I think the endpoint should just return an error early if already approved.

[marius-mather]

looks good to me