Add external links for tasks with plugin api

app/ExternalLink/BaseLink.php

@@ -0,0 +1,44 @@
+<?php
+
+namespace Kanboard\ExternalLink;
+
+use Kanboard\Core\Base;
+
+/**
+ * Base Link
+ *
+ * @package  externalLink
+ * @author   Frederic Guillot
+ */
+abstract class BaseLink extends Base
+{
+    /**
+     * URL
+     *
+     * @access protected
+     * @var string
+     */
+    protected $url = '';
+
+    /**
+     * Get link URL
+     *
+     * @access public
+     * @return string
+     */
+    public function getUrl()
+    {
+        return $this->url;
+    }
+
+    /**
+     * Set link URL
+     *
+     * @access public
+     * @param  string $url
+     */
+    public function setUrl($url)
+    {
+        $this->url = $url;
+    }
+}