feat: implement billing system with Pally integration

- Added billing models and repository for handling bills.
- Introduced BillingService to manage payment initiation and bill creation.
- Updated user service to remove ticket-related functionality.
- Refactored settings to include new billing-related fields.
- Removed ticket-related handlers and schemas.
- Added new billing handlers for processing payments.
- Updated database schema with new bills table and status enum.
- Enhanced utility functions to calculate prices considering discounts.
- Introduced prehandling for non-private messages.
- Updated main application to initialize new billing services and repositories.

misc/utils.py

@@ -170,14 +170,18 @@ def convert_duration_to_timedelta(duration: SubscriptionDuration) -> timedelta:
 
 
 def calculate_price(subscription: SubscriptionPlan):
-    return (
-        (subscription.devices * settings.per_device_cost)
-        + (
-            int(subscription.whitelists) * settings.whitelist_cost
-            if subscription.devices < settings.whitelist_device_threshold
-            else 0
+    return math.ceil(
+        (
+            (subscription.devices * settings.per_device_cost)
+            + (
+                int(subscription.whitelists) * settings.whitelist_cost
+                if subscription.devices < settings.whitelist_device_threshold
+                else 0
+            )
         )
-    ) * convert_duration_to_int(subscription.duration)
+        * convert_duration_to_int(subscription.duration)
+        * subscription.discount
+    )
 
 
 def get_discount(months) -> float: