docs: add authentication example

docs_src/examples/authentication/db.py

@@ -0,0 +1,15 @@
+from fastapi import Depends
+from sqlalchemy.ext.asyncio import async_sessionmaker, create_async_engine
+
+from fastapi_toolsets.db import create_db_context, create_db_dependency
+
+DATABASE_URL = "postgresql+asyncpg://postgres:postgres@localhost:5432/postgres"
+
+engine = create_async_engine(url=DATABASE_URL, future=True)
+async_session_maker = async_sessionmaker(bind=engine, expire_on_commit=False)
+
+get_db = create_db_dependency(session_maker=async_session_maker)
+get_db_context = create_db_context(session_maker=async_session_maker)
+
+
+SessionDep = Depends(get_db)