make component types hierarchial

shimatta_kenkyusho/parts/migrations/0012_componenttype_parent_class.py

@@ -0,0 +1,19 @@
+# Generated by Django 3.2.5 on 2022-11-11 20:18
+
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('parts', '0011_auto_20220110_1812'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='componenttype',
+            name='parent_class',
+            field=models.ForeignKey(blank=True, null=True, on_delete=django.db.models.deletion.PROTECT, related_name='child_classes', to='parts.componenttype'),
+        ),
+    ]