added AsJson step decorator

Author: DavertMik

src/Codeception/Step/AsJson.php

@@ -0,0 +1,31 @@
+<?php
+
+namespace Codeception\Step;
+
+use Codeception\Lib\ModuleContainer;
+use Codeception\Util\Template;
+
+class AsJson extends Action implements GeneratedStep
+{
+    public function run(ModuleContainer $container = null)
+    {
+        $container->getModule('REST')->haveHttpHeader('Content-Type', 'application/json');
+        $resp = parent::run($container);
+        return json_decode($resp, true);
+    }
+
+    public static function getTemplate(Template $template)
+    {
+        $action = $template->getVar('action');
+
+        // should only be applied to send* methods
+        if (strpos($action, 'send') !== 0) return;
+
+        $conditionalDoc = "* JSON response will be automatically  decoded \n     " . $template->getVar('doc');
+
+        return $template
+            ->place('doc', $conditionalDoc)
+            ->place('action', $action . 'AsJson')
+            ->place('step', 'AsJson');
+    }
+}