user preference fixes and improvements

cookbook/migrations/0040_auto_20200502_1433.py

@@ -0,0 +1,22 @@
+# Generated by Django 3.0.5 on 2020-05-02 12:33
+
+import annoying.fields
+from django.conf import settings
+from django.db import migrations
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        migrations.swappable_dependency(settings.AUTH_USER_MODEL),
+        ('cookbook', '0039_recipebook_shared'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='userpreference',
+            name='user',
+            field=annoying.fields.AutoOneToOneField(on_delete=django.db.models.deletion.CASCADE, primary_key=True, serialize=False, to=settings.AUTH_USER_MODEL),
+        ),
+    ]