Make user in UserHostingKey model nullable

hosting/migrations/0055_auto_20190701_1614.py

@@ -0,0 +1,22 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.9.4 on 2019-07-01 16:14
+from __future__ import unicode_literals
+
+from django.conf import settings
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('hosting', '0054_auto_20190508_2141'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='userhostingkey',
+            name='user',
+            field=models.ForeignKey(blank=True, null=True, on_delete=django.db.models.deletion.CASCADE, to=settings.AUTH_USER_MODEL),
+        ),
+    ]