* Use ASGI root_path when it is provided and openapi_prefix is empty.
* Strip trailing slashes from root_path.
* Please mypy.
* Fix extending openapi test.
* 📝 Add docs and tutorial for using root_path behind a proxy
* ♻️ Refactor application root_path logic, use root_path, deprecate openapi_prefix
* ✅ Add tests for Behind a Proxy with root_path
* ♻️ Refactor test
* 📝 Update/add docs for Sub-applications and Behind a Proxy
* 📝 Update Extending OpenAPI with openapi_prefix parameter
* ✅ Add test for deprecated openapi_prefix
Co-authored-by: Sebastián Ramírez <tiangolo@gmail.com>