Fix notification delivery duplication5

[abk-tech]

Summary

Implemented notification delivery resilience improvements to prevent duplicate outbound messages during retries and high-volume event bursts.

Changes

Notification Deduplication

• Added notification deduplication using event identifiers/unique keys where supported.
• Prevents duplicate notifications from being dispatched when the same event is processed multiple times.
• Ensures idempotent notification handling across retry scenarios.

Retry & Backoff Improvements

• Replaced retry behavior with capped exponential backoff.
• Added configurable retry limits to prevent unbounded retry loops.
• Reduced risk of provider throttling and excessive outbound traffic.

Provider Isolation

• Isolated provider failures to prevent a single provider error from impacting unrelated notification deliveries.
• Improved error handling and logging around notification dispatch operations.
• Ensured notification processing can continue for other providers/events when one provider fails.

Configuration Updates

• Added notification reliability configuration options.
• Extended configuration validation to support new retry and deduplication settings.

Test Coverage

• Added tests for duplicate event submissions.
• Added tests for provider failure scenarios.
• Added tests validating retry limits and backoff behavior.

Impact

• Prevents duplicate notifications during retries and event bursts.
• Reduces likelihood of provider rate limiting or blocking.
• Improves notification delivery reliability and fault tolerance.
• Ensures failures are contained and do not affect unrelated notification flows.

closes: #35

[MaryammAli]

LGTM
thank you for ur contribution