Add audit system core with event handling and subject conversion

- Implemented `AuditEvent` class to represent audit events.
- Added `AuditEvent2Trail` for converting events to audit trails.
- Introduced `Subject` and `SubjectConverterManager` for subject conversion.
- Created contracts like `SubjectConverterInterface` and `AuditEvent2TrailInterface`.
- Developed `AuditEventSubscriber` to persist audit events using `AuditTrailPersister`.
- Included test classes for core audit services and components.

src/Bundle/ChillMainBundle/Audit/AuditEvent.php

@@ -0,0 +1,27 @@
+<?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\MainBundle\Audit;
+
+use Symfony\Contracts\Translation\TranslatableInterface;
+
+readonly class AuditEvent
+{
+    public function __construct(
+        public string $action,
+        /**
+         * @var list<object>
+         */
+        public array $subjects = [],
+        public string|TranslatableInterface $description = '',
+        public array $metadata = [],
+    ) {}
+}