Added API/Endpoint abstract class

- (re)Added Endpoints folder to both API and Router
- fixed syntax in namespaces
- xhr.responseJSON is returned to the fail()
- fixed Router endpoints (view in browser, cron,...)

lib/Router/Endpoints/Queue.php

@@ -0,0 +1,16 @@
+<?php
+namespace MailPoet\Router\Endpoints;
+
+use MailPoet\Cron\Daemon;
+
+if(!defined('ABSPATH')) exit;
+
+class Queue {
+  const ENDPOINT = 'queue';
+  const ACTION_RUN = 'run';
+
+  static function run($data) {
+    $queue = new Daemon($data);
+    $queue->run();
+  }
+}

lib/Router/Endpoints/Subscription.php

@@ -0,0 +1,24 @@
+<?php
+namespace MailPoet\Router\Endpoints;
+
+use MailPoet\Subscription as UserSubscription;
+
+if(!defined('ABSPATH')) exit;
+
+class Subscription {
+  const ENDPOINT = 'subscription';
+
+  static function confirm($data) {
+    $subscription = new UserSubscription\Pages('confirm', $data);
+    $subscription->confirm();
+  }
+
+  static function manage($data) {
+    $subscription = new UserSubscription\Pages('manage', $data);
+  }
+
+  static function unsubscribe($data) {
+    $subscription = new UserSubscription\Pages('unsubscribe', $data);
+    $subscription->unsubscribe();
+  }
+}

lib/Router/Endpoints/Track.php

@@ -0,0 +1,23 @@
+<?php
+namespace MailPoet\Router\Endpoints;
+
+use MailPoet\Statistics\Track\Clicks;
+use MailPoet\Statistics\Track\Opens;
+
+if(!defined('ABSPATH')) exit;
+
+class Track {
+  const ENDPOINT = 'track';
+  const ACTION_CLICK = 'click';
+  const ACTION_OPEN = 'open';
+
+  static function click($data) {
+    $clicks = new Clicks($data);
+    $clicks->track();
+  }
+
+  static function open($data) {
+    $opens = new Opens($data);
+    $opens->track();
+  }
+}

lib/Router/Endpoints/ViewInBrowser.php

@@ -0,0 +1,16 @@
+<?php
+namespace MailPoet\Router\Endpoints;
+
+use MailPoet\Newsletter\ViewInBrowser as NewsletterViewInBrowser;
+
+if(!defined('ABSPATH')) exit;
+
+class ViewInBrowser {
+  const ENDPOINT = 'view_in_browser';
+  const ACTION_VIEW = 'view';
+
+  static function view($data) {
+    $viewer = new NewsletterViewInBrowser($data);
+    $viewer->view();
+  }
+}