fix: use groupBy correctly eliminating the need for a new method

src/Helper/MyParcelCollection.php

@@ -268,8 +268,12 @@ public function createConcepts(): self
         $newConsignments = $this->where('consignment_id', '!=', null)->toArray();
         $this->addMissingReferenceId();
 
+        $grouped = $this->where('consignment_id', null)->groupBy(function($item) {
+            return $item->getApiKey() . ($item->hasSender() ? '-sender' : '');
+        });
+
         /* @var MyParcelCollection $consignments */
-        foreach ($this->where('consignment_id', null)->groupInto(['apiKey', 'sender']) as $consignments) {
+        foreach ($grouped as $consignments) {
             $headers = MyParcelRequest::HEADER_CONTENT_TYPE_SHIPMENT;
             if ($consignments->first()->hasSender()) {
                 $headers += MyParcelRequest::HEADER_SET_CUSTOM_SENDER;

src/Support/Collection.php

@@ -773,33 +773,6 @@ public function groupBy($groupBy, $preserveKeys = false)
         return $result;
     }
 
-    /**
-     * Group this collection into separate collections by one or more fields.
-     * Returns an array of separate collections grouped by md5 encoded string of the grouped fields.
-     *
-     * @param array $by
-     * @return array
-     */
-    public function groupInto(array $by): array {
-        $result = [];
-
-        foreach ($this->items as $item) {
-            $group = '';
-            foreach ($by as $key) {
-                $group .= $this->helper->data_get($item, $key);
-            }
-            $group = md5($group);
-
-            if (!isset($result[$group])) {
-                $result[$group] = new static();
-            }
-
-            $result[$group]->push($item);
-        }
-
-        return $result;
-    }
-
     /**
      * Key an associative array by a field or using a callback.
      *