feat(sub): handling upgrade/downgrade

rw integration and /me endpoints are left

services/plans.py

@@ -1,6 +1,7 @@
 from repositories.addons import AddonsRepository
 from repositories.pricing import PricingRepository
 from schemas.plans import AddonData, OrderDetails, PricingPlans
+from services.subscriptions import calculate_order_total
 
 
 async def get_pricing_model(addons_repo: AddonsRepository, pricing_repo: PricingRepository):
@@ -21,4 +22,9 @@ async def calculate_price(
     *, addons_repo: AddonsRepository, order: OrderDetails, pricing: PricingPlans
 ) -> float:
     addons = [await addons_repo.get_by_id(a) for a in order.addons]
-    return order.devices * pricing.device_price + sum([a.price for a in addons])
+    return calculate_order_total(
+        pricing,
+        order.devices,
+        [addon.id for addon in addons],
+        order.duration_days,
+    )