[7.x] Add lineItemPriceHook hook (#1157)

* Created price hook from a lineItem perspective

* Let's not document this for now.

* Doh! I removed the wrong bit.

* Add back the note.

* Code Style

---------

Co-authored-by: Jan Willem Rigters <jrigters@steets.nl>
Co-authored-by: Duncan McClean <duncan@doublethree.digital>

src/Orders/Calculator/LineItemCalculator.php

@@ -41,6 +41,8 @@ public function handle(Order $order, Closure $next)
                 if ($product->purchasableType() === ProductType::Product) {
                     if (SimpleCommerce::$productPriceHook) {
                         $productPrice = (SimpleCommerce::$productPriceHook)($order, $product);
+                    } elseif (SimpleCommerce::$lineItemPriceHook) {
+                        $productPrice = (SimpleCommerce::$lineItemPriceHook)($lineItem);
                     } else {
                         $productPrice = $product->price();
                     }

src/SimpleCommerce.php

@@ -23,6 +23,8 @@ class SimpleCommerce
 
     public static $productVariantPriceHook;
 
+    public static $lineItemPriceHook;
+
     public static function version(): string
     {
         if (app()->environment('testing')) {
@@ -200,4 +202,11 @@ public static function productVariantPriceHook(Closure $callback): self
 
         return new static;
     }
+
+    public static function lineItemPriceHook(Closure $callback): self
+    {
+        static::$lineItemPriceHook = $callback;
+
+        return new static;
+    }
 }