add Bidirectional trait

src/Fields/Settings/Bidirectional.php

@@ -0,0 +1,29 @@
+<?php
+
+/**
+ * Copyright (c) Vincent Klaiber
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ *
+ * @see https://github.com/vinkla/extended-acf
+ */
+
+declare(strict_types=1);
+
+namespace Extended\ACF\Fields\Settings;
+
+trait Bidirectional
+{
+    /**
+     * Create a bidirectional relationship between two or more fields. Note: this requires setting a custom key for each related field via the `key` method, and passing those related fields' keys to this method.
+     * @see https://www.advancedcustomfields.com/resources/bidirectional-relationships/ for details & caveats
+     */
+    public function bidirectional(array|string $keys): static
+    {
+        $this->settings['bidirectional'] = 1;
+        $this->settings['bidirectional_target'] = is_array($keys) ? $keys : [$keys];
+
+        return $this;
+    }
+}