feat(devops): dont allow deleting a git group if it has children

ref: #776

app/devops/migrations/0014_alter_gitgroup_parent_group.py

@@ -0,0 +1,27 @@
+# Generated by Django 5.1.9 on 2025-05-29 03:48
+
+import django.db.models.deletion
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("devops", "0013_alter_gitgroup_id_alter_gitgroup_model_notes_and_more"),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name="gitgroup",
+            name="parent_group",
+            field=models.ForeignKey(
+                blank=True,
+                help_text="Parent Git Group this repository belongs to.",
+                null=True,
+                on_delete=django.db.models.deletion.PROTECT,
+                related_name="+",
+                to="devops.gitgroup",
+                verbose_name="Parent Group",
+            ),
+        ),
+    ]