Add migration to change user_id to customuser_id in legacy code

Pertains to djangocms_blog

membership/migrations/0008_change_user_id_to_customer_id_in_djangocms_blog.py

@@ -0,0 +1,13 @@
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+    dependencies = [('membership', '0007_auto_20180213_0128'),
+                    ('djangocms_blog', '0032_auto_20180109_0023'),
+                    ]
+
+    operations = [
+        migrations.RunSQL(
+            "ALTER TABLE djangocms_blog_authorentriesplugin_authors "
+            "RENAME COLUMN user_id TO customuser_id;"),
+    ]