feat(promo): Добавлены промокоды на скидку в процентах

bot/handlers/user/subscription/payment_discount_helper.py

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+"""
+Helper функция для применения скидок к платежам
+Используется всеми платежными обработчиками
+"""
+import logging
+from typing import Optional, Tuple
+from sqlalchemy.ext.asyncio import AsyncSession
+from db.dal import active_discount_dal
+
+
+async def apply_discount_to_payment(
+    session: AsyncSession,
+    user_id: int,
+    original_price: float,
+    promo_code_service=None
+) -> Tuple[float, Optional[float], Optional[int]]:
+    """
+    Apply active discount to payment if exists.
+
+    Returns:
+        (final_price, discount_amount, promo_code_id)
+    """
+    if not promo_code_service:
+        return original_price, None, None
+
+    active_discount = await active_discount_dal.get_active_discount(session, user_id)
+    if not active_discount:
+        return original_price, None, None
+
+    # Calculate discounted price
+    final_price, discount_amount = promo_code_service.calculate_discounted_price(
+        original_price, active_discount.discount_percentage
+    )
+
+    logging.info(
+        f"Applying {active_discount.discount_percentage}% discount to payment for user {user_id}: "
+        f"{original_price} -> {final_price}"
+    )
+
+    return final_price, discount_amount, active_discount.promo_code_id