Set up message delivery guarantees and failure handling E5.

[chendiblessing]

Description: Establish robust message delivery guarantees to ensure reliable communication. Implement mechanisms for message acknowledgment and retries to achieve either at-least-once or exactly-once delivery semantics. Define strategies for handling message failures and ensure the server can recover and resend messages as needed.

Acceptance Criteria:

• Implemented acknowledgment mechanisms for message delivery.
• Configured retry logic and failure handling strategies.
• Documented delivery guarantees (e.g., at-least-once, exactly-once).