Add subcription feature

shared/subscription/coupons.py

@@ -3,7 +3,7 @@ Coupon system for subscription discounts and promotions.
 Supports trial extensions, percentage discounts, and fixed amount discounts.
 """
 from dataclasses import dataclass
-from datetime import datetime
+from datetime import datetime, timezone
 from enum import Enum
 from typing import Optional
 
@@ -32,7 +32,7 @@ class Coupon:
 
     def is_valid(self) -> bool:
         """Check if coupon is currently valid"""
-        now = datetime.utcnow()
+        now = datetime.now(timezone.utc)
 
         # Check if active
         if not self.active:
@@ -60,7 +60,7 @@ class Coupon:
         if not self.active:
             return False, "Coupon is inactive"
 
-        now = datetime.utcnow()
+        now = datetime.now(timezone.utc)
 
         if now < self.valid_from:
             return False, "Coupon is not yet valid"
@@ -98,7 +98,7 @@ def calculate_trial_end_date(base_trial_days: int, extension_days: int) -> datet
     """Calculate trial end date with coupon extension"""
     from datetime import timedelta
     total_days = base_trial_days + extension_days
-    return datetime.utcnow() + timedelta(days=total_days)
+    return datetime.now(timezone.utc) + timedelta(days=total_days)
 
 
 def format_discount_description(coupon: Coupon) -> str: