[feat] add basic domain

repository/user.py

@@ -0,0 +1,21 @@
+from collections.abc import Iterable
+
+from domain.user import User
+from usecase.interface import UserRepository
+
+
+class InMemoryUserRepository(UserRepository):
+    def __init__(self, users: Iterable[User] | None = None) -> None:
+        self._users = {user.id: user for user in users or ()}
+
+    def get(self, user_id: str) -> User | None:
+        return self._users.get(user_id)
+
+    def get_by_email(self, email: str) -> User | None:
+        for user in self._users.values():
+            if user.email == email:
+                return user
+        return None
+
+    def save(self, user: User) -> None:
+        self._users[user.id] = user