refactor/The Data Foundation

[fulleni]

The data models need to be updated to support this new layer of information.

• User Model:
  • Add new fields for segmentation: lastSeenAt: DateTime?, sessionCount: int, etc.
• New UserNotificationSettings Model:
  • A new model, linked to the User, to store the user's preferences for different categories of engagement notifications (e.g., allowPromotions, allowSuggestions).
• PushNotificationPayload Model:
  • This model is already well-suited for this system and requires no changes. Its generic data map is perfect for handling deep-links from any type of campaign.
• PushNotificationSubscriptionDeliveryType Enum:
  • This enum remains perfectly valid for its original purpose: user-configured, filter-based automated alerts like digests. It will coexist with the new system for admin/marketing-driven engagement.