Add Google grant

src/Grant/CustomGrantFactory.php

@@ -36,6 +36,8 @@ protected function registerDefaultGrant($name)
 
         if ($name == 'facebook') {
             $class = 'KangarooRewards\\OAuth2\\Client\\Grant\\' . $class;
+        } elseif ($name == 'google') {
+            $class = 'KangarooRewards\\OAuth2\\Client\\Grant\\' . $class;
         } else {
             $class = 'League\\OAuth2\\Client\\Grant\\' . $class;
         }

src/Grant/Google.php

@@ -0,0 +1,39 @@
+<?php
+
+/**
+ * @license http://opensource.org/licenses/MIT MIT
+ * @link http://thephpleague.com/oauth2-client/ Documentation
+ * @link https://packagist.org/packages/league/oauth2-client Packagist
+ * @link https://github.com/thephpleague/oauth2-client GitHub
+ */
+
+namespace KangarooRewards\OAuth2\Client\Grant;
+
+use League\OAuth2\Client\Grant\AbstractGrant;
+
+/**
+ * Represents a Google grant.
+ *
+ * @link http://tools.ietf.org/html/rfc6749#section-1.3.3 Resource Owner Password Credentials (RFC 6749, §1.3.3)
+ */
+class Google extends AbstractGrant
+{
+    /**
+     * @inheritdoc
+     */
+    protected function getName()
+    {
+        return 'google';
+    }
+
+    /**
+     * @inheritdoc
+     */
+    protected function getRequiredRequestParameters()
+    {
+        return [
+            'username',
+            'google_token',
+        ];
+    }
+}