Enh: Add LinkedIn auth

This will implement the ability to use LinkedIn auth to login.

protected/humhub/modules/user/authclient/LinkedIn.php

@@ -0,0 +1,116 @@
+<?php
+
+/**
+ * @link https://www.humhub.org/
+ * @copyright Copyright (c) 2017 HumHub GmbH & Co. KG
+ * @license https://www.humhub.com/licences
+ */
+
+namespace humhub\modules\user\authclient;
+
+use yii\authclient\OAuth2;
+use yii\web\HttpException;
+use Yii;
+
+class LinkedIn extends \yii\authclient\clients\LinkedIn
+{
+
+    /**
+     * @inheritdoc
+     */
+    protected function defaultViewOptions()
+    {
+        return [
+            'popupWidth' => 860,
+            'popupHeight' => 480,
+            'cssIcon' => 'fa fa-linkedin',
+            'buttonBackgroundColor' => '#395697',
+        ];
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public $authUrl = 'https://www.linkedin.com/oauth/v2/authorization';
+
+    /**
+     * {@inheritdoc}
+     */
+    public $tokenUrl = 'https://www.linkedin.com/oauth/v2/accessToken';
+
+    /**
+     * {@inheritdoc}
+     */
+    public $apiBaseUrl = 'https://api.linkedin.com/v1';
+
+    /**
+     * {@inheritdoc}
+     */
+    public $attributeNames = [
+        'id',
+        'email-address',
+        'first-name',
+        'last-name',
+        'public-profile-url',
+    ];
+
+    /**
+     * {@inheritdoc}
+     */
+    public function init()
+    {
+        parent::init();
+        if ($this->scope === null) {
+            $this->scope = implode(' ', [
+                'r_basicprofile',
+                'r_emailaddress',
+            ]);
+        }
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    protected function defaultNormalizeUserAttributeMap()
+    {
+        return [
+            'email' => 'email-address',
+            'first_name' => 'first-name',
+            'last_name' => 'last-name',
+        ];
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    protected function initUserAttributes()
+    {
+        return $this->api('people/~:(' . implode(',', $this->attributeNames) . ')', 'GET');
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function applyAccessTokenToRequest($request, $accessToken)
+    {
+        $data = $request->getData();
+        $data['oauth2_access_token'] = $accessToken->getToken();
+        $request->setData($data);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    protected function defaultName()
+    {
+        return 'linkedin';
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    protected function defaultTitle()
+    {
+        return 'LinkedIn';
+    }
+}