Performs two important error handling functions on an
AuthenticationException raised from the authentication
layer:
Maps handler errors onto message bundle strings for display to user.
Determines the next webflow state by comparing handler errors.
Stores all flow execution state in ClientFlowExecutionKey, which effectively stores execution state on the
client in a form parameter when a view is rendered.
This is DefaultCasDelegatingWebflowEventResolver,
which handles the initial authentication attempt and calls upon a number of
embedded resolvers to produce the next event in the authentication flow.