feat(firewall): add safeguarded rule creation

Signed-off-by: Sebastian Krupinski <krupinski01@gmail.com>

core/lib/Service/FirewallRuleConflictException.php

@@ -0,0 +1,15 @@
+<?php
+
+declare(strict_types=1);
+
+namespace KTXC\Service;
+
+final class FirewallRuleConflictException extends \RuntimeException
+{
+    public function __construct(
+        public readonly string $conflictCode,
+        string $message
+    ) {
+        parent::__construct($message);
+    }
+}