🗃️(backend) fix storage_location for existing BBB AWS documents

The `storage location` field was introduced in a previous release and filled
with a default value "AWS_S3". However, the correct enum value is "AWS".

Author: wilbrdt

src/backend/marsha/bbb/migrations/0026_classroomdocument_fix_storage_location.py

@@ -0,0 +1,23 @@
+# Generated by Django 5.0.9 on 2025-06-11 17:34
+
+from django.db import migrations
+
+from marsha.core.defaults import AWS_S3
+
+
+def fix_storage_location_to_aws(apps, schema_editor):
+    """Update the storage_location field for existing classroom documents."""
+    ClassroomDocument = apps.get_model("bbb", "ClassroomDocument")
+    ClassroomDocument.objects.filter(storage_location="AWS_S3").update(
+        storage_location=AWS_S3
+    )
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("bbb", "0025_classroomdocument_fill_storage_location"),
+    ]
+
+    operations = [
+        migrations.RunPython(fix_storage_location_to_aws, migrations.RunPython.noop),
+    ]