core: add uuid to user, use as sub for OpenID

passbook/core/migrations/0006_user_uuid.py

@@ -0,0 +1,20 @@
+# Generated by Django 2.1.4 on 2018-12-09 17:58
+
+import uuid
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('passbook_core', '0005_auto_20181127_1522'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='user',
+            name='uuid',
+            field=models.UUIDField(default=uuid.uuid4, editable=False),
+        ),
+    ]