Added extended stats aggregation

Aggregation/ExtendedStatsAggregation.php

+<?php
+
+/*
+ * This file is part of the ONGR package.
+ *
+ * (c) NFQ Technologies UAB <info@nfq.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace ONGR\ElasticsearchBundle\DSL\Aggregation;
+
+use ONGR\ElasticsearchBundle\DSL\Aggregation\Type\MetricTrait;
+use ONGR\ElasticsearchBundle\DSL\ScriptAwareTrait;
+
+/**
+ * Class representing Extended stats aggregation.
+ */
+class ExtendedStatsAggregation extends AbstractAggregation
+{
+    use MetricTrait;
+    use ScriptAwareTrait;
+
+    /**
+     * @var int
+     */
+    private $sigma;
+
+    /**
+     * @return int
+     */
+    public function getSigma()
+    {
+        return $this->sigma;
+    }
+
+    /**
+     * @param int $sigma
+     */
+    public function setSigma($sigma)
+    {
+        $this->sigma = $sigma;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getType()
+    {
+        return 'extended_stats';
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getArray()
+    {
+        $out = [];
+
+        if ($this->getField()) {
+            $out['field'] = $this->getField();
+        } elseif ($this->getScript()) {
+            $out['script'] = $this->getScript();
+        } else {
+            throw new \LogicException('Extended stats aggregation must have field or script set.');
+        }
+
+        if ($this->getSigma()) {
+            $out['sigma'] = $this->getSigma();
+        }
+
+        return $out;
+    }
+}