✨ Add support for function return type annotations to declare the response_model (#1436)

Co-authored-by: Sebastián Ramírez <tiangolo@gmail.com>

docs_src/response_model/tutorial001_01.py

@@ -0,0 +1,27 @@
+from typing import List, Union
+
+from fastapi import FastAPI
+from pydantic import BaseModel
+
+app = FastAPI()
+
+
+class Item(BaseModel):
+    name: str
+    description: Union[str, None] = None
+    price: float
+    tax: Union[float, None] = None
+    tags: List[str] = []
+
+
+@app.post("/items/")
+async def create_item(item: Item) -> Item:
+    return item
+
+
+@app.get("/items/")
+async def read_items() -> List[Item]:
+    return [
+        Item(name="Portal Gun", price=42.0),
+        Item(name="Plumbus", price=32.0),
+    ]