Created new action to track visits, which returns an empty pixel

module/Common/src/Response/PixelResponse.php

@@ -0,0 +1,33 @@
+<?php
+declare(strict_types=1);
+
+namespace Shlinkio\Shlink\Common\Response;
+
+use Psr\Http\Message\StreamInterface;
+use Zend\Diactoros\Response;
+use Zend\Diactoros\Stream;
+
+class PixelResponse extends Response
+{
+    private const BASE_64_IMAGE = 'R0lGODlhAQABAJAAAP8AAAAAACH5BAUQAAAALAAAAAABAAEAAAICBAEAOw==';
+    private const CONTENT_TYPE = 'image/gif';
+
+    public function __construct(int $status = 200, array $headers = [])
+    {
+        $headers['content-type'] = self::CONTENT_TYPE;
+        parent::__construct($this->createBody(), $status, $headers);
+    }
+
+    /**
+     * Create the message body.
+     *
+     * @return StreamInterface
+     */
+    private function createBody(): StreamInterface
+    {
+        $body = new Stream('php://temp', 'wb+');
+        $body->write(\base64_decode(self::BASE_64_IMAGE));
+        $body->rewind();
+        return $body;
+    }
+}