Protect Contributor deletion to prevent major data loss

partners/migrations/0019_auto_20170624_2003.py

+# -*- coding: utf-8 -*-
+# Generated by Django 1.10.3 on 2017-06-24 18:03
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('partners', '0018_merge_20170624_1943'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='membershipagreement',
+            name='offered_yearly_contribution',
+            field=models.SmallIntegerField(default=0, help_text="Yearly contribution in euro's (€)"),
+        ),
+    ]

scipost/migrations/0058_auto_20170624_2003.py

+# -*- coding: utf-8 -*-
+# Generated by Django 1.10.3 on 2017-06-24 18:03
+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 = [
+        ('scipost', '0057_merge_20170624_1943'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='contributor',
+            name='user',
+            field=models.OneToOneField(on_delete=django.db.models.deletion.PROTECT, to=settings.AUTH_USER_MODEL),
+        ),
+    ]

scipost/models.py

@@ -37,7 +37,7 @@ class Contributor(models.Model):
     Permissions determine the sub-types.
     username, password, email, first_name and last_name are inherited from User.
     """
-    user = models.OneToOneField(User, on_delete=models.CASCADE, unique=True)
+    user = models.OneToOneField(User, on_delete=models.PROTECT, unique=True)
     invitation_key = models.CharField(max_length=40, blank=True)
     activation_key = models.CharField(max_length=40, blank=True)
     key_expires = models.DateTimeField(default=timezone.now)