feat(domain): value objects, entities, port traits with tests

crates/domain/src/value_objects/mod.rs

@@ -0,0 +1,9 @@
+mod email;
+mod password;
+mod role;
+mod user_id;
+
+pub use email::Email;
+pub use password::PasswordHash;
+pub use role::Role;
+pub use user_id::UserId;