feat: additional custom discount applied to total price

tests/Form/Admin/Groups/AccommodationBookingTypeTest.php

@@ -73,6 +73,42 @@ class AccommodationBookingTypeTest extends TestCase
         self::assertSame(['email', 'firstName', 'groupName', 'lastName'], $properties);
     }
 
+    /**
+     * The label is printed verbatim on the customer's PDF, so a percentage without one is
+     * refused — and in the Default group, so that even a draft cannot store the pair half-set.
+     */
+    public function testTotalDiscountRequiresALabel(): void
+    {
+        $booking = new AccommodationBooking();
+        $booking->setTotalDiscount(5);
+
+        $violations = $this->validate($booking, ['Default']);
+
+        self::assertCount(1, $violations);
+        self::assertSame('totalDiscountLabel', $violations[0]->getPropertyPath());
+    }
+
+    public function testALabelledTotalDiscountPassesValidation(): void
+    {
+        $booking = new AccommodationBooking();
+        $booking->setTotalDiscount(5);
+        $booking->setTotalDiscountLabel('Treuerabatt');
+
+        self::assertCount(0, $this->validate($booking, ['Default']));
+    }
+
+    /**
+     * The reverse is harmless — without a percentage the label never reaches a breakdown row —
+     * so it is deliberately left valid rather than blocking a half-typed edit.
+     */
+    public function testALabelWithoutAPercentageIsAccepted(): void
+    {
+        $booking = new AccommodationBooking();
+        $booking->setTotalDiscountLabel('Treuerabatt');
+
+        self::assertCount(0, $this->validate($booking, ['Default']));
+    }
+
     /**
      * @return string[]
      */