remove create_home_folder() & ensure_home_folder()
now: on_user_created() and on_user_login both() call provision_if_needed()
which calls **create_personal_drive_atomic()**
add a helper to find Personal drive for a user and also it's root directorry
prepare identity service for external users, support of:
- magic_link (url challenge via email)
- self issued oidc (eventually social login)
- open cloud mesh
- AuthzCacheLifecycleHook — invalidates the user_groups_cache Moka entry on logout/delete.
- SessionRevocationLifecycleHook — explicit per-session firing of on_user_logout (currently per-call); session revocation inside the user-delete transaction.
- DeletionMode-driven policy in HomeFolderLifecycleHook::on_user_deleted (trash vs hard-delete based on AdminDelete / GdprPurge).
- Refactor delete_user_admin to expose a transaction handle so on_user_deleted can abort atomically.