feat(external users): email sanity + mock SMTP

- SMTP has a mock to enable end to end test and validate the whole path
     (via OXICLOUD_SMTP_MOCK)
    - add email normalisation ( including punicode)
    - api to share to external user

src/application/services/mod.rs

@@ -15,6 +15,7 @@ pub mod file_upload_service;
 pub mod file_use_case_factory;
 pub mod folder_service;
 pub mod i18n_application_service;
+pub mod magic_link_invite_service;
 pub mod music_service;
 pub mod nextcloud_file_id_service;
 pub mod nextcloud_login_flow_service;