Update doc for SQLALchemy2 adapter

examples/sqlalchemy-oauth/app/db.py

@@ -1,35 +1,42 @@
-import databases
-import sqlalchemy
+from typing import AsyncGenerator
+
+from fastapi import Depends
 from fastapi_users.db import (
     SQLAlchemyBaseOAuthAccountTable,
     SQLAlchemyBaseUserTable,
     SQLAlchemyUserDatabase,
 )
+from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine
 from sqlalchemy.ext.declarative import DeclarativeMeta, declarative_base
+from sqlalchemy.orm import relationship, sessionmaker
 
 from app.models import UserDB
 
-DATABASE_URL = "sqlite:///./test.db"
-database = databases.Database(DATABASE_URL)
+DATABASE_URL = "sqlite+aiosqlite:///./test.db"
 Base: DeclarativeMeta = declarative_base()
 
 
 class UserTable(Base, SQLAlchemyBaseUserTable):
+    oauth_accounts = relationship("OAuthAccount")
+
+
+class OAuthAccountTable(SQLAlchemyBaseOAuthAccountTable, Base):
     pass
 
 
-class OAuthAccount(SQLAlchemyBaseOAuthAccountTable, Base):
-    pass
+engine = create_async_engine(DATABASE_URL, connect_args={"check_same_thread": False})
+async_session_maker = sessionmaker(engine, class_=AsyncSession, expire_on_commit=False)
 
 
-engine = sqlalchemy.create_engine(
-    DATABASE_URL, connect_args={"check_same_thread": False}
-)
-Base.metadata.create_all(engine)
-
-users = UserTable.__table__
-oauth_accounts = OAuthAccount.__table__
+async def create_db_and_tables():
+    async with engine.begin() as conn:
+        await conn.run_sync(Base.metadata.create_all)
 
 
-async def get_user_db():
-    yield SQLAlchemyUserDatabase(UserDB, database, users, oauth_accounts)
+async def get_async_session() -> AsyncGenerator[AsyncSession, None]:
+    async with async_session_maker() as session:
+        yield session
+
+
+async def get_user_db(session: AsyncSession = Depends(get_async_session)):
+    yield SQLAlchemyUserDatabase(UserDB, session, UserTable, OAuthAccountTable)