[16.x] refactor: allow null coupon and promotion code IDs (#1808)

* refactor(AllowsCoupons): allow null coupon and promotion code IDs

Update method signatures to accept null values for couponId and promotionCodeId parameters to handle cases where these values might be unset

* fix ci

* Revert "fix ci"

This reverts commit f6ca1b1.

* fix ci

Author: nguyentranchung

src/Concerns/AllowsCoupons.php

@@ -11,15 +11,11 @@ trait AllowsCoupons
 
     /**
      * The coupon ID being applied.
-     *
-     * @var string|null
      */
     public ?string $couponId = null;
 
     /**
      * The promotion code ID being applied.
-     *
-     * @var string|null
      */
     public ?string $promotionCodeId = null;
 
@@ -33,10 +29,9 @@ trait AllowsCoupons
     /**
      * The coupon ID to be applied.
      *
-     * @param  string  $couponId
      * @return $this
      */
-    public function withCoupon(string $couponId)
+    public function withCoupon(?string $couponId)
     {
         $this->couponId = $couponId;
 
@@ -46,10 +41,9 @@ public function withCoupon(string $couponId)
     /**
      * The promotion code ID to apply.
      *
-     * @param  string  $promotionCodeId
      * @return $this
      */
-    public function withPromotionCode(string $promotionCodeId)
+    public function withPromotionCode(?string $promotionCodeId)
     {
         $this->promotionCodeId = $promotionCodeId;