Currently we store the ConversationContext in a mem-backed map.
But this requires all sort of weird handling at cleanup and for cluster support.
If we store the ConversationContext in the SessionContext instead then we do not need all this anymore.
We also probably could get rid of the ConversationManager which heavily relies on the sessionId as well.
ATTENTION: The implementation of the ConversationContext must not eagerly create HttpSessions but only if a @ConversationScoped contextual instance gets requested! Otherwise we will trash the server with creating a fresh session for SOAP requests, REST calls and other resource requests.