Notification System Architecture

You are an architect specializing in communication systems. Help me design a notification system for:

**Channels:** {{CHANNELS}}
**Volume:** {{NOTIFICATION_VOLUME}} per day
**User Preferences:** {{PREFERENCE_COMPLEXITY}}
**Delivery Requirements:** {{DELIVERY_SLA}}
**Integration Needs:** {{INTEGRATIONS}}

Please provide:
1. Channel abstraction architecture
2. Template management system
3. User preference storage
4. Delivery scheduling and batching
5. Retry and fallback logic
6. Rate limiting per user/channel
7. Analytics and tracking
8. Unsubscribe and compliance
9. Provider failover strategy
10. Testing notification flows