✨ Add support for not needing ... as default value in required Query(), Path(), Header(), etc. (#4906)

* ✨ Do not require default value in Query(), Path(), Header(), etc

* 📝 Update source examples for docs with default and required values

* ✅ Update tests with new default values and not required Ellipsis

* 📝 Update docs for Query params and update info about default value, required, Ellipsis

docs_src/additional_status_codes/tutorial001.py

@@ -1,4 +1,4 @@
-from typing import Optional
+from typing import Union
 
 from fastapi import Body, FastAPI, status
 from fastapi.responses import JSONResponse
@@ -10,7 +10,9 @@ items = {"foo": {"name": "Fighters", "size": 6}, "bar": {"name": "Tenders", "siz
 
 @app.put("/items/{item_id}")
 async def upsert_item(
-    item_id: str, name: Optional[str] = Body(None), size: Optional[int] = Body(None)
+    item_id: str,
+    name: Union[str, None] = Body(default=None),
+    size: Union[int, None] = Body(default=None),
 ):
     if item_id in items:
         item = items[item_id]