init

app/domain/users/services.py

@@ -0,0 +1,9 @@
+from __future__ import annotations
+
+from app.domain.users.entities import User
+from app.domain.users.exceptions import UserAlreadyExists
+
+
+def ensure_unique_email(*, existing_user: User | None) -> None:
+    if existing_user is not None:
+        raise UserAlreadyExists("User with this email already exists.")