Add services and tests for associated entities management

Implemented services to provide associated persons and third parties for accompanying periods and their works. Included comprehensive tests to ensure proper functionality and associations.

src/Bundle/ChillPersonBundle/Service/AccompanyingPeriod/ProvidePersonsAssociated.php

@@ -0,0 +1,34 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * Chill is a software for social workers
+ *
+ * For the full copyright and license information, please view
+ * the LICENSE file that was distributed with this source code.
+ */
+
+namespace Chill\PersonBundle\Service\AccompanyingPeriod;
+
+use Chill\PersonBundle\Entity\AccompanyingPeriod;
+use Chill\PersonBundle\Entity\AccompanyingPeriodParticipation;
+use Chill\PersonBundle\Entity\Person;
+
+/**
+ * Provide persons associated with an accompanying period.
+ */
+class ProvidePersonsAssociated
+{
+    /**
+     * @return list<Person>
+     */
+    public function getPersonsAssociated(AccompanyingPeriod $period): array
+    {
+        return array_values(
+            $period->getCurrentParticipations()
+                ->map(fn (AccompanyingPeriodParticipation $participation) => $participation->getPerson())
+                ->toArray()
+        );
+    }
+}