feat(api): can grant external user (via email)

- add possibility to grant an external user.
    - route /api/users/{id} added (rate limited for security)
    - security: start route limitation for external users
        ex: they must not browse /api/users/{id} nor addressbook

src/interfaces/api/handlers/mod.rs

@@ -21,6 +21,7 @@ pub mod search_handler;
 pub mod share_handler;
 pub mod subject_group_handler;
 pub mod trash_handler;
+pub mod users_handler;
 pub mod webdav_handler;
 pub mod wopi_handler;