✨ Add support for shared/top-level parameters (dependencies, tags, etc) (#2434)

* ✨ Add Default and DefaultPlaceholder data structures

to handle defaults and overrides

* ✨ Add utils to get values by priority handling DefaultPlaceholders

* ✨ Add support for top-level parameters in FastAPI, APIRouter, include_router

including: prefix, tags, dependencies, deprecated, include_in_schema, responses, default_response_class, callbacks

* ♻️ Update openapi utils to handle DefaultPlaceholder for response_class

* 📝 Update bigger-application example code to use top-level params

and showcase them in APIRouter, FastAPI, include_router

* 📝 Update docs for Bigger Applications, include diagrams, top-level params

* 🔥 Simplify code and docs for callbacks as default_response_class is no longer required

* 📝 Add docs for top-level dependencies, in FastAPI()

* 📝 Add docs reference to top-level dependencies in docs for decorator

* ✅ Update/increase tests for Bigger Applications including shared parameters

* ✅ Add tests for top-level dependencies in FastAPI()

* ✅ Add tests for internal DefaultPlaceholder

* ✅ Update/increase tests for callbacks with top-level parameters

* ✅ Add LOTS of tests covering branches and cases for shared parameters

in top-level FastAPI, path operations, include_router, APIRouter, its path operations, nested include_router, nested APIRouter, and its path operations

* 🎨 Format/reorder parameters for consistency in FastAPI, APIRouter, include_router

docs_src/openapi_callbacks/tutorial001.py

@@ -1,7 +1,6 @@
 from typing import Optional
 
 from fastapi import APIRouter, FastAPI
-from fastapi.responses import JSONResponse
 from pydantic import BaseModel, HttpUrl
 
 app = FastAPI()
@@ -23,7 +22,7 @@ class InvoiceEventReceived(BaseModel):
     ok: bool
 
 
-invoices_callback_router = APIRouter(default_response_class=JSONResponse)
+invoices_callback_router = APIRouter()
 
 
 @invoices_callback_router.post(