feat: enhance subscription management with discount calculations and update support messages

misc/utils.py

@@ -1,3 +1,4 @@
+import math
 import urllib.parse
 from datetime import UTC, datetime, timedelta
 from random import choice
@@ -179,8 +180,15 @@ def calculate_price(subscription: SubscriptionPlan):
     ) * convert_duration_to_int(subscription.duration)
 
 
+def get_discount(months) -> float:
+    if months <= 0:
+        return 0
+    calculated = 5 * (math.log2(months / 3) + 1)
+    return max(0, calculated)
+
+
 def format_subscription_link(link: str | None = None):
-    return f"<code>{link or '...'}</code>"
+    return f"<code>{link or texts.NOTHING_PLACEHOLDER}</code>"
 
 
 def format_share_deep_link(link: str):