fix: Remove Person.core_member field

See #33

people/migrations/0019_remove_person_core_member.py

@@ -0,0 +1,17 @@
+# Generated by Django 2.2.10 on 2020-06-24 11:14
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('people', '0018_require_user_email'),
+    ]
+
+    operations = [
+        migrations.RemoveField(
+            model_name='person',
+            name='core_member',
+        ),
+    ]