- Added `NotifyBillingStatusChangedAsync` method to `IRealtimeNotifier` for notifying clients about changes in billing status.
- Updated `BillingConfigResumer` to call the new notification method after modifying billing configurations, ensuring users receive real-time updates.
- Enhanced `ListUsersQueryHandler` to include a `BillingPendingReview` property in `UserSummaryDto`, indicating if a user has a pending payment request awaiting confirmation.
- Refactored various command handlers to utilize `AdvisoryLock` for managing concurrent requests, preventing race conditions in billing operations.
- Updated tests to cover new notification behaviors and ensure proper functionality in billing status management.
- Introduced a new `DiscountTierDto` to represent volume discount tiers, allowing roles with a config quota at or above specified thresholds to receive discounts on pricing.
- Updated the `PricingSettingsDto` to include a list of discount tiers, enhancing the pricing model to support more flexible pricing strategies.
- Modified the `GetPricingSettingsQueryHandler` and `UpdatePricingSettingsCommandHandler` to handle discount tiers, ensuring they are correctly retrieved and updated in the database.
- Enhanced validation in `UpdatePricingSettingsCommandValidator` to enforce uniqueness and progressive discount tiers, preventing invalid configurations.
- Updated frontend components to support the new discount tier functionality, including forms for adding and managing discount tiers in the admin interface.
- Revised API documentation to reflect the new discount tier features and their usage in pricing settings.
- Introduced billing capabilities, allowing users to request payments for subscription periods (3/6/12 months) with admin approval via Telegram.
- Updated role management to include a `BillingEnabled` property, preventing billing for admin roles.
- Enhanced the `CreateRoleCommand` and `UpdateRoleCommand` to accept billing parameters, ensuring proper handling during role creation and updates.
- Added new endpoints for billing management and integrated billing checks into VPN config creation to enforce payment requirements.
- Updated related services, models, and tests to support the new billing features, ensuring comprehensive coverage and functionality.
- Enhanced documentation to reflect the new billing processes and role management changes.