feat(userLifecycle): prepare external service identity

prepare identity service for external users, support of:
        - magic_link (url challenge via email)
        - self issued oidc (eventually social login)
        - open cloud mesh

src/application/services/mod.rs

@@ -6,6 +6,7 @@ pub mod blob_lifecycle_service;
 pub mod calendar_service;
 pub mod contact_service;
 pub mod device_auth_service;
+pub mod external_identity_service;
 pub mod favorites_service;
 pub mod file_lifecycle_service;
 pub mod file_management_service;