fix hmac calculation in complete purchase response

Author: aozisik

src/Messages/CompletePurchaseResponse.php

@@ -77,11 +77,18 @@ public function getCardToken()
 
     private function everyPayRequestHmac()
     {
+        $options = SignedDataOptions::gateway(
+            $this->request->getSecret()
+        )->dontInclude([
+            'utf8',
+            'hmac',
+            '_method',
+            'authenticity_token'
+        ]);
+
         return SignedData::make(
             $this->data['request'],
-            SignedDataOptions::gateway(
-                $this->request->getSecret()
-            )
+            $options
         )['hmac'];
     }
 

src/Support/SignedDataOptions.php

@@ -31,6 +31,17 @@ public static function backend($secret)
         ]);
     }
 
+    public function dontInclude(array $fields)
+    {
+        $this->options['dontInclude'] = array_unique(
+            array_merge(
+                $this->options['dontInclude'] ?? [],
+                $fields
+            )
+        );
+        return $this;
+    }
+
     public function shouldHmacInclude($field)
     {
         return !in_array($field, $this->options['dontInclude']);