Sync fastapi docs from 50fa3f7c on 2026-01-11

docs_src/conditional_openapi/tutorial001_py39.py

@@ -0,0 +1,16 @@
+from fastapi import FastAPI
+from pydantic_settings import BaseSettings
+
+
+class Settings(BaseSettings):
+    openapi_url: str = "/openapi.json"
+
+
+settings = Settings()
+
+app = FastAPI(openapi_url=settings.openapi_url)
+
+
+@app.get("/")
+def root():
+    return {"message": "Hello World"}