* Add AccessDeniedPath support to the OIDC/OAuth2/Twitter providers
* Update the code documentation and remove an unnecessary call to SignOutAsync()
* Introduce a new AccessDenied event and move most of the access denied handling logic to RemoteAuthenticationHandler
* Add ReturnUrlParameter support to RemoteAuthenticationHandler
* Remove AccessDeniedException and introduce RemoteAuthenticationHandler.HandleAccessDeniedErrorAsync()
* Use OriginalPath instead of Request.Path
* Update obsolete code comments
* Add unit tests for the new AccessDenied event
* Allow customizing the access denied path/return URL/return URL parameter from the AccessDenied event