I improved ClientReturnUrl backref to Client.
I added error handling into idp authentication algorithm.
I added the oauth2 exceptions handler. It supports only json responses for now.
I added support for idp authenticate login_token append when other query parameters already exist.
I implemented return_url validation for oauth2 idp authentication.
I fully implemented form urlencoded exception handling.
I added error_description encoding for form url encoded redirect.
I isolated response / exception objects into roa controller integration tests.