Consumer logic

1. Validate message
   1. in case of error - write message to log, move to error queue
2. Ensure that entity exists
   1. in case of error - write message to log, move to error queue 
3. Validate transition
   1. Check service request status (must be 'active')
      1. in case of error - write message to log, set message as processed
4. Update service request status to completed (see DEPRECATED - Referrals State Model - V1)
5. Add transition to Event Manager