Feature: Creating Cart Service, Cart Events, Save For Later functionality, Adding Filament Views for viewing abandoned carts

src/Cart/Exceptions/InvalidCouponException.php

@@ -0,0 +1,19 @@
+<?php
+
+namespace Modules\Core\Cart\Exceptions;
+
+use RuntimeException;
+
+/**
+ * Thrown by CartService::applyCoupon() when the given code doesn't match any
+ * currently-active, non-exhausted Discount — Lunar's own
+ * Discounts::validateCoupon() only returns a bool, it has no matching
+ * exception type of its own to reuse here.
+ */
+class InvalidCouponException extends RuntimeException
+{
+    public function __construct(public readonly string $code)
+    {
+        parent::__construct("The coupon code \"{$code}\" is not valid.");
+    }
+}