fix author

order-events/app/events/billing/append_enrollment.py

@@ -96,7 +96,7 @@ def lambda_handler(event: EventBridgeEvent, context: LambdaContext) -> bool:
         pass
 
     try:
-        author = data['author']
+        author = data.get('author')
         course_id = data['course']['id']
         course = course_layer.collection.get_items(
             KeyPair(
@@ -118,15 +118,21 @@ def lambda_handler(event: EventBridgeEvent, context: LambdaContext) -> bool:
                 'user': pick(('id', 'name'), data['user']),
                 'course': pick(('id', 'name'), data['course']),
                 'unit_price': course['unit_price'],
-                'author': {
-                    'id': author['user_id'],
-                    'name': author['name'],
-                },
                 # Post-migration: uncomment the following line
                 # 'enrolled_at': data['created_at'],
                 'enrolled_at': data['create_date'],
                 'created_at': now_,
-            },
+            }
+            | (
+                {
+                    'author': {
+                        'id': author['user_id'],
+                        'name': author['name'],
+                    }
+                }
+                if author
+                else {}
+            ),
             cond_expr='attribute_not_exists(sk)',
         )
     except Exception as exc: