Add migration.

biscuit/core/migrations/0006_make_unique.py

+# Generated by Django 2.2.3 on 2019-07-24 21:26
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('core', '0005_person_short_name'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='group',
+            name='name',
+            field=models.CharField(max_length=30, unique=True, verbose_name='Long name of group'),
+        ),
+        migrations.AlterField(
+            model_name='group',
+            name='short_name',
+            field=models.CharField(max_length=8, unique=True, verbose_name='Short name of group'),
+        ),
+        migrations.AlterField(
+            model_name='person',
+            name='import_ref',
+            field=models.CharField(blank=True, editable=False, max_length=64, unique=True, verbose_name='Reference ID of import source'),
+        ),
+        migrations.AlterField(
+            model_name='person',
+            name='short_name',
+            field=models.CharField(blank=True, max_length=5, unique=True, verbose_name='Short name'),
+        ),
+    ]