core: change provider to one-to-one field

passbook/core/migrations/0002_auto_20181125_1638.py

@@ -0,0 +1,19 @@
+# Generated by Django 2.1.3 on 2018-11-25 16:38
+
+import django.db.models.deletion
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('passbook_core', '0001_initial'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='application',
+            name='provider',
+            field=models.OneToOneField(default=None, null=True, on_delete=django.db.models.deletion.SET_DEFAULT, to='passbook_core.Provider'),
+        ),
+    ]

passbook/core/models.py

@@ -49,7 +49,8 @@ class Application(RuleModel):
     name = models.TextField()
     launch_url = models.URLField(null=True, blank=True)
     icon_url = models.TextField(null=True, blank=True)
-    provider = models.ForeignKey('Provider', null=True, default=None, on_delete=models.SET_DEFAULT)
+    provider = models.OneToOneField('Provider', null=True,
+                                    default=None, on_delete=models.SET_DEFAULT)
     skip_authorization = models.BooleanField(default=False)
 
     objects = InheritanceManager()