Moves current API under JSON namespace

lib/API/JSON/SuccessResponse.php

@@ -0,0 +1,21 @@
+<?php
+namespace MailPoet\API\JSON;
+
+if(!defined('ABSPATH')) exit;
+
+class SuccessResponse extends Response {
+  public $data;
+
+  function __construct($data = array(), $meta = array(), $status = self::STATUS_OK) {
+    parent::__construct($status, $meta);
+    $this->data = $data;
+  }
+
+  function getData() {
+    if($this->data === null) return null;
+
+    return array(
+      'data' => $this->data
+    );
+  }
+}