feat: add ClassifiedAd domain entity

domain/marketplace/__init__.py

@@ -0,0 +1 @@
+from .classified_ad import ClassifiedAd

domain/marketplace/classified_ad.py

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+from dataclasses import dataclass
+from decimal import Decimal
+from uuid import UUID
+
+
+@dataclass(frozen=True)
+class ClassifiedAd:
+    id: UUID
+    _ownerId: UUID
+    title: str
+    text: str
+    _price: Decimal