ActiveMQ + Megabus: Investigate retry policies + deadletter

• 1. Investigate if we can ack only in the end of processing a message (either by configuration or manually)
• 2. If so, confirm that message goes back to the queue when a worker dies unexpectedly
• 3. Check if throwing an error is sufficient to return the message to the queue
• Investigate support for deadletters:
  • Is there anything prebuilt on the megabus library?
  • How do we configure it on activemq?
  • Is there any builtin support to move messages back to the main queue, ie in the activeMQ admin ui?
• Check retrial policy alternatives: is there's any retry mechanism builtin in the megabus library or do we need to implement it ourselves