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/Subject.php

@@ -0,0 +1,28 @@
+<?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;
+
+class Subject
+{
+    public function __construct(
+        public string $type,
+        /**
+         * @var array<string, string|number|\Stringable>
+         */
+        public array $identifiers,
+    ) {}
+
+    public function asArray(): array
+    {
+        return [...$this->identifiers, 't' => $this->type];
+    }
+}