[6.x] Fix shipping method fieldtype (#1028)

* Fix shipping method fieldtype

* Fix tests

Author: duncanmcclean

src/Fieldtypes/ShippingMethodFieldtype.php

@@ -60,7 +60,7 @@ public function toItemArray($value)
         $site = Site::selected();
 
         $shippingMethod = SimpleCommerce::shippingMethods($site->handle())
-            ->where('class', $value)
+            ->where('handle', $value)
             ->first();
 
         if (! $shippingMethod) {
@@ -83,7 +83,7 @@ public function preProcessIndex($data)
             $site = Site::selected();
 
             $shippingMethod = SimpleCommerce::shippingMethods($site->handle())
-                ->where('class', $item)
+                ->where('handle', $item)
                 ->first();
 
             if (! $shippingMethod) {

tests/Fieldtypes/ShippingMethodFieldtypeTest.php

@@ -40,7 +40,7 @@
 });
 
 test('can return as item array', function () {
-    $toItemArray = $this->fieldtype->toItemArray(FreeShipping::class);
+    $toItemArray = $this->fieldtype->toItemArray(FreeShipping::handle());
 
     expect($toItemArray)->toBeArray();
 
@@ -51,7 +51,7 @@
 });
 
 test('can preprocess index', function () {
-    $preProcessIndex = $this->fieldtype->preProcessIndex(FreeShipping::class);
+    $preProcessIndex = $this->fieldtype->preProcessIndex(FreeShipping::handle());
 
     expect($preProcessIndex)->toBeString();
     expect('Free Shipping')->toBe($preProcessIndex);