add prevent_overlapping_time_entries setting to organization

when enabled users are blocked from creating or editing new time entries that are overlapping with other time entries

app/Exceptions/Api/OverlappingTimeEntryApiException.php

@@ -0,0 +1,10 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Exceptions\Api;
+
+class OverlappingTimeEntryApiException extends ApiException
+{
+    public const string KEY = 'overlapping_time_entry';
+}