feat: migrate mcq answer from int to list

tutorial/migrations/0006_migrate_mcq_answers.py

@@ -0,0 +1,28 @@
+from django.db import migrations
+
+
+def migrate_mcq_answers(apps, schema_editor):
+    Exercise = apps.get_model("tutorial", "Exercise")
+    for ex in Exercise.objects.filter(type="mcq"):
+        if isinstance(ex.data.get("answer"), int):
+            ex.data["answer"] = [ex.data["answer"]]
+            ex.save()
+
+
+def reverse_migrate_mcq_answers(apps, schema_editor):
+    Exercise = apps.get_model("tutorial", "Exercise")
+    for ex in Exercise.objects.filter(type="mcq"):
+        if isinstance(ex.data.get("answer"), list) and len(ex.data["answer"]) == 1:
+            ex.data["answer"] = ex.data["answer"][0]
+            ex.save()
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('tutorial', '0005_alter_exercise_type'),
+    ]
+
+    operations = [
+        migrations.RunPython(migrate_mcq_answers, reverse_migrate_mcq_answers),
+    ]