Restrict deletion of identifier_definition to prevent errors and ensure data integrity

- Updated foreign key constraint on `chill_person_identifier.definition_id` to use `ON DELETE RESTRICT` instead of `ON DELETE CASCADE`.
- Adjusted migration script to handle both the upgrade and downgrade paths for the new restriction.

src/Bundle/ChillPersonBundle/migrations/Version20250924101621.php

@@ -0,0 +1,53 @@
+<?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\Migrations\Person;
+
+use Doctrine\DBAL\Schema\Schema;
+use Doctrine\Migrations\AbstractMigration;
+
+/**
+ * Restrict the deletion of identifier_definition to avoid risk of error.
+ *
+ * An identifier definition can only be removed if there aren't any identifier defined.
+ */
+final class Version20250924101621 extends AbstractMigration
+{
+    public function getDescription(): string
+    {
+        return 'Restrict the deletion of identifier_definition';
+    }
+
+    public function up(Schema $schema): void
+    {
+        $this->addSql(<<<'SQL'
+            ALTER TABLE chill_person_identifier DROP CONSTRAINT fk_bca5a36bd11ea911
+        SQL);
+        $this->addSql(<<<'SQL'
+            ALTER TABLE chill_person_identifier ADD CONSTRAINT fk_bca5a36bd11ea911
+            FOREIGN KEY (definition_id) REFERENCES chill_person_identifier_definition (id)
+            on delete restrict
+        SQL);
+
+    }
+
+    public function down(Schema $schema): void
+    {
+        $this->addSql(<<<'SQL'
+            ALTER TABLE chill_person_identifier DROP CONSTRAINT fk_bca5a36bd11ea911
+        SQL);
+        $this->addSql(<<<'SQL'
+            ALTER TABLE chill_person_identifier ADD CONSTRAINT fk_bca5a36bd11ea911
+            FOREIGN KEY (definition_id) REFERENCES chill_person_identifier_definition (id)
+            on delete cascade
+        SQL);
+    }
+}