feat: add Money value object

domain/marketplace/__init__.py

@@ -1,3 +1,4 @@
 from .classified_ad import ClassifiedAd as ClassifiedAd
 from .classified_ad_id import ClassifiedAdId as ClassifiedAdId
+from .money import Money as Money
 from .user_id import UserId as UserId

domain/marketplace/money.py

@@ -0,0 +1,7 @@
+from dataclasses import dataclass
+from decimal import Decimal
+
+
+@dataclass(frozen=True)
+class Money:
+    amount: Decimal