Refactor code structure for improved readability and maintainability

app/main.py

@@ -0,0 +1,57 @@
+import asyncio
+import logging
+from collections.abc import AsyncIterator
+from contextlib import asynccontextmanager
+
+from fastapi import FastAPI
+from faststream.rabbit import Channel, RabbitBroker
+
+from app.api import router
+from app.config import settings
+from app.db import close_database, session_factory
+from app.messaging import declare_topology
+from app.outbox import OutboxPublisher
+
+logging.basicConfig(
+    level=logging.INFO,
+    format="%(asctime)s %(levelname)s %(name)s: %(message)s",
+)
+
+
+@asynccontextmanager
+async def lifespan(_: FastAPI) -> AsyncIterator[None]:
+    broker = RabbitBroker(
+        settings.rabbitmq_url,
+        default_channel=Channel(publisher_confirms=True, on_return_raises=True),
+    )
+    await broker.start()
+    await declare_topology(broker)
+
+    stop_event = asyncio.Event()
+    publisher = OutboxPublisher(
+        session_factory,
+        broker,
+        batch_size=settings.outbox_batch_size,
+        poll_interval=settings.outbox_poll_interval,
+        publish_timeout=settings.outbox_publish_timeout,
+    )
+    publisher_task = asyncio.create_task(publisher.run(stop_event))
+
+    try:
+        yield
+    finally:
+        stop_event.set()
+        try:
+            await asyncio.wait_for(
+                publisher_task,
+                timeout=settings.outbox_publish_timeout + settings.outbox_poll_interval,
+            )
+        except TimeoutError:
+            publisher_task.cancel()
+            await asyncio.gather(publisher_task, return_exceptions=True)
+        await broker.stop()
+        await close_database()
+
+
+app = FastAPI(title=settings.app_name, version="1.0.0", lifespan=lifespan)
+app.include_router(router)