Create on-to-many relationship.

bikeshop_project/core/migrations/0011_auto_20160531_0233.py

@@ -0,0 +1,22 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.9.4 on 2016-05-31 02:33
+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 = [
+        ('core', '0010_membership_member'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='membership',
+            name='member',
+            field=models.ForeignKey(blank=True, null=True, on_delete=django.db.models.deletion.CASCADE, related_name='memberships', to=settings.AUTH_USER_MODEL),
+        ),
+    ]

bikeshop_project/core/models.py

@@ -15,10 +15,10 @@ class Membership(models.Model):
         blank=False,
         null=True
     )
-    member = models.OneToOneField(
+    member = models.ForeignKey(
         'registration.Member',
         on_delete=models.CASCADE,
-        related_name='membership',
+        related_name='memberships',
         blank=True,
         null=True
     )