database refactor and remove redundant code

app/database.py

@@ -1,8 +1,11 @@
+from asyncio import current_task
+
 from typing import AsyncGenerator
 
 from fastapi import HTTPException
+from fastapi.encoders import jsonable_encoder
 from sqlalchemy.exc import SQLAlchemyError
-from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine
+from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine, async_scoped_session
 from sqlalchemy.orm import sessionmaker
 
 from app import config
@@ -14,16 +17,18 @@ engine = create_async_engine(
     url,
     future=True,
     echo=True,
+    json_serializer=jsonable_encoder,
 )
 
 # expire_on_commit=False will prevent attributes from being expired
 # after commit.
-async_session = sessionmaker(engine, expire_on_commit=False, class_=AsyncSession)
+async_session_factory = sessionmaker(engine, expire_on_commit=False, class_=AsyncSession)
+AsyncScopedSession = async_scoped_session(async_session_factory, scopefunc=current_task)
 
 
 # Dependency
 async def get_db() -> AsyncGenerator:
-    async with async_session() as session:
+    async with async_session_factory() as session:
         try:
             yield session
             await session.commit()
@@ -35,3 +40,4 @@ async def get_db() -> AsyncGenerator:
             raise http_ex
         finally:
             await session.close()
+