Fix domain relation deletion

src/DomainRelation.php

@@ -118,7 +118,7 @@ function ($e) {
 
     public function pre_deleteItem()
     {
-        if (in_array([self::BELONGS, self::MANAGE], $this->fields['id'])) {
+        if (in_array($this->fields['id'], [self::BELONGS, self::MANAGE])) {
            //keep defaults
             return false;
         }

tests/functional/DomainRelation.php

@@ -0,0 +1,58 @@
+<?php
+
+/**
+ * ---------------------------------------------------------------------
+ *
+ * GLPI - Gestionnaire Libre de Parc Informatique
+ *
+ * http://glpi-project.org
+ *
+ * @copyright 2015-2023 Teclib' and contributors.
+ * @copyright 2003-2014 by the INDEPNET Development Team.
+ * @licence   https://www.gnu.org/licenses/gpl-3.0.html
+ *
+ * ---------------------------------------------------------------------
+ *
+ * LICENSE
+ *
+ * This file is part of GLPI.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ *
+ * ---------------------------------------------------------------------
+ */
+
+namespace tests\units;
+
+use DbTestCase;
+
+class DomainRelation extends DbTestCase
+{
+    public function testDeleteProtectedRelations()
+    {
+        $this->login();
+
+        $relation = new \DomainRelation();
+        $this->integer($unprotected_id = $relation->add([
+            'name' => __FUNCTION__
+        ]))->isGreaterThan(0);
+
+        // Should not be able to delete the domain relations added to GLPI by default
+        $this->boolean($relation->delete(['id' => \DomainRelation::BELONGS]))->isFalse();
+        $this->boolean($relation->delete(['id' => \DomainRelation::MANAGE]))->isFalse();
+
+        // Should be able to delete the domain relation added by the test
+        $this->boolean($relation->delete(['id' => $unprotected_id]))->isTrue();
+    }
+}