OIDC exception handling

If authentication is unsuccessful, the RealMe Authorisation Endpoint returns the customer to the redirection URI specified in the authentication request with the following error response parameters:

Response Parameter	Mandatory/ Optional	Description
error	Mandatory	Error code
error_description	Mandatory	Human-readable ASCII encoded text description of the error
state	Mandatory	Returns same value provided in authentication request.

The following is an example of an OIDC authentication response for an unsuccessful authentication journey:

Location: https://sample.govt.nz/SignIn/CallbackCodeOidc?

error=invalid_request
&error_description= AADB2C90117%3A+The+scope+%27Unsupported%27+provided+in+the+request+is+not+supported.%0D%0ACorrelation+ID%3A+e014e109-0c68-4757-b511-e81fd3b01450%0D%0ATimestamp%3A+2024-08-08+20%3A35%3A56Z%0D%0A

&state=af0ifjsldkj

The following table provides key error codes and descriptions:

Error Code	Error Description
unsupported_response_type	RealMe does not support obtaining an authorisation code using this method.
access_denied	User exited from the RealMe journey or RealMe denied the request. Refer to the error description for further information.
invalid_request	The request is missing a required parameter, includes an invalid parameter value, includes a parameter more than once, or is otherwise malformed.
server_error	RealMe encountered an unexpected condition that prevented it from fulfilling the request. (This error code is needed because a 500 Internal Server Error HTTP status code cannot be returned to the client via an HTTP redirect.)