feat: replace custom discount with absolute value in favor of percentage

src/Service/AccommodationBookingBreakdownCalculator.php

@@ -43,7 +43,8 @@ class AccommodationBookingBreakdownCalculator
     public function withDiscounts(AccommodationBooking $booking, array $breakdown): array
     {
         // The labels carry their own "Rabatt" prefix so that every row renders as plain
-        // {label} {percent} %, including the freely named discount on the total below.
+        // {label} {percent} %, while the freely named discount on the total below is a fixed
+        // amount and renders as its label alone.
         $buckets = [
             ['Rabatt Unterkunft', $booking->getAccommodationDiscount(), (int) ($breakdown['basePrice'] ?? 0) + (int) ($breakdown['additionalPersonsPrice'] ?? 0)],
             ['Rabatt Verpflegung', $booking->getBoardServiceDiscount(), (int) ($breakdown['boardPrice'] ?? 0)],
@@ -70,15 +71,15 @@ class AccommodationBookingBreakdownCalculator
         // computing the new total, where the stored one is still the outdated value.
         $subtotal = (int) ($breakdown['total'] ?? 0) - $discountSum;
 
-        // Compounds on the already-reduced subtotal rather than on the gross total: the discount
-        // is granted on what the customer would otherwise pay, not on a figure no longer asked.
-        $totalDiscountAmount = self::discountAmount($subtotal, $booking->getTotalDiscount());
+        // A fixed sum rather than a percentage, subtracted after the section discounts. Clamped to
+        // what is left of the subtotal so that a discount larger than the price cannot produce a
+        // negative total, the same guard BookingSummaryAssembler applies to vouchers.
+        $totalDiscountAmount = min($booking->getTotalDiscountAmount() ?? 0, max(0, $subtotal));
 
         $breakdown['discounts'] = $discounts;
         $breakdown['totalDiscountDetails'] = 0 !== $totalDiscountAmount
             ? [
                 'label' => (string) $booking->getTotalDiscountLabel(),
-                'percent' => $booking->getTotalDiscount(),
                 'amount' => $totalDiscountAmount,
             ]
             : null;