✨ 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/path_params_numeric_validations/tutorial001.py

@@ -1,4 +1,4 @@
-from typing import Optional
+from typing import Union
 
 from fastapi import FastAPI, Path, Query
 
@@ -7,8 +7,8 @@ app = FastAPI()
 
 @app.get("/items/{item_id}")
 async def read_items(
-    item_id: int = Path(..., title="The ID of the item to get"),
-    q: Optional[str] = Query(None, alias="item-query"),
+    item_id: int = Path(title="The ID of the item to get"),
+    q: Union[str, None] = Query(default=None, alias="item-query"),
 ):
     results = {"item_id": item_id}
     if q: