What this PR changes/adds

Fixes for:

• ConsumerContractNegotiationManagerImpl.processAccepting did not pass the current Policy as part of the RemoteMessage when dispatching, causing an NPE during policy evaluation.
• JsonObjectToPolicyTransformer did not deserialize assignee and assigner if the policy type is an agreement, which is required by DSP
• DspHttpRemoteMessageDispatcherImpl did not report the HTTP error code
• DspRequestHandlerImpl reported the incorrect validation context
• ContractNegotiation did not allow for a valid state transition (OFFERED)
• ContractNegotistion should not allow transitions from FINALIZED to TERMINATED

Linked Issue(s)

Closes #4543