Migrate structure metadata

arkindex/documents/migrations/0028_structure_metadata.py

+from django.db import migrations
+from arkindex_common.enums import MetaType
+
+
+def structure_metadata(apps, schema_editor):
+    """
+    Update reference
+    """
+    MetaData = apps.get_model('documents', 'MetaData')
+    MetaData.objects.filter(name='Reference').update(type=MetaType.Structure)
+
+
+def reverse_migration(apps, schema_editor):
+    MetaData = apps.get_model('documents', 'MetaData')
+    MetaData.objects.filter(type=MetaType.Structure).update(type=MetaType.Text)
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('documents', '0027_classification_best'),
+    ]
+
+    operations = [
+        migrations.RunPython(structure_metadata, reverse_migration)
+    ]