feat: add FastAPI, Entity base class, and health check endpoint

domain/framework/entity.py

@@ -0,0 +1,18 @@
+from abc import ABC
+from dataclasses import replace
+from typing import Self
+
+from domain.marketplace.domain_event import DomainEvent
+
+
+class Entity(ABC):
+    _events: tuple[DomainEvent, ...] = ()
+
+    def raise_event(self, event: DomainEvent) -> Self:
+        return replace(self, _events=(*self._events, event))
+
+    def get_changes(self) -> tuple[DomainEvent, ...]:
+        return self._events
+
+    def clear_changes(self) -> Self:
+        return replace(self, _events=())