✨ Allow disabling docs UIs by disabling OpenAPI (#1421)

* ✨ Allow disabling docs UIs by disabling openapi_url

* 📝 Add docs for disabling OpenAPI and docs in prod or other environments

* ✅ Add tests for disabling OpenAPI and docs

docs_src/conditional_openapi/tutorial001.py

@@ -0,0 +1,16 @@
+from fastapi import FastAPI
+from pydantic import BaseSettings
+
+
+class Settings(BaseSettings):
+    openapi_url: str = "/openapi.json"
+
+
+settings = Settings()
+
+app = FastAPI(openapi_url=settings.openapi_url)
+
+
+@app.get("/")
+def root():
+    return {"message": "Hello World"}