Add data migration for label's subclass

backend/api/migrations/0021_auto_20211220_2355.py

@@ -0,0 +1,60 @@
+from django.db import migrations
+
+
+def assign_label_to_subclass(apps, schema_editor):
+    Label = apps.get_model('api', 'Label')
+    DocType = apps.get_model('api', 'DocType')
+    SpanType = apps.get_model('api', 'SpanType')
+    for label in Label.objects.all():
+        project_type = label.project.project_type
+        if project_type.endswith('Classification'):
+            model = DocType
+        else:
+            model = SpanType
+        label.delete()
+        model(
+            id=label.id,
+            text=label.text,
+            prefix_key=label.prefix_key,
+            suffix_key=label.suffix_key,
+            project=label.project,
+            background_color=label.background_color,
+            text_color=label.text_color,
+            created_at=label.created_at,
+            updated_at=label.updated_at
+        ).save()
+
+
+def assign_subclass_to_label(apps, schema_editor):
+    Label = apps.get_model('api', 'Label')
+    DocType = apps.get_model('api', 'DocType')
+    SpanType = apps.get_model('api', 'SpanType')
+    for model in [DocType, SpanType]:
+        for label in model.objects.all():
+            new_label = Label(
+                id=label.id,
+                text=label.text,
+                prefix_key=label.prefix_key,
+                suffix_key=label.suffix_key,
+                project=label.project,
+                background_color=label.background_color,
+                text_color=label.text_color,
+                created_at=label.created_at,
+                updated_at=label.updated_at
+            )
+            label.delete()
+            new_label.save()
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('api', '0020_auto_20211220_2327'),
+    ]
+
+    operations = [
+        migrations.RunPython(
+            code=assign_label_to_subclass,
+            reverse_code=assign_subclass_to_label
+        ),
+    ]