📝 Update docs and examples for Response Model with Return Type Annotations, and update runtime error (#5873)

docs_src/response_model/tutorial003_05.py

@@ -0,0 +1,13 @@
+from typing import Union
+
+from fastapi import FastAPI, Response
+from fastapi.responses import RedirectResponse
+
+app = FastAPI()
+
+
+@app.get("/portal", response_model=None)
+async def get_portal(teleport: bool = False) -> Union[Response, dict]:
+    if teleport:
+        return RedirectResponse(url="https://www.youtube.com/watch?v=dQw4w9WgXcQ")
+    return {"message": "Here's your interdimensional portal."}