Allow NULL in unique charfields.

biscuit/core/migrations/0012_allow_null.py

+# Generated by Django 2.2.4 on 2019-08-17 12:08
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('core', '0011_default_school'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='person',
+            name='import_ref',
+            field=models.CharField(blank=True, editable=False, max_length=64, null=True, verbose_name='Reference ID of import source'),
+        ),
+        migrations.AlterField(
+            model_name='person',
+            name='short_name',
+            field=models.CharField(blank=True, max_length=5, null=True, verbose_name='Short name'),
+        ),
+    ]

biscuit/core/models.py

@@ -44,7 +44,7 @@ class Person(SchoolRelated):
         'Additional name(s)'), max_length=30, blank=True)
 
     short_name = models.CharField(verbose_name=_(
-        'Short name'), max_length=5, blank=True)
+        'Short name'), max_length=5, blank=True, null=True)
 
     street = models.CharField(verbose_name=_(
         'Street'), max_length=30, blank=True)
@@ -69,7 +69,7 @@ class Person(SchoolRelated):
     photo = models.ImageField(verbose_name=_('Photo'), blank=True, null=True)
 
     import_ref = models.CharField(verbose_name=_(
-        'Reference ID of import source'), max_length=64, blank=True, editable=False)
+        'Reference ID of import source'), max_length=64, blank=True, null=True, editable=False)
 
     guardians = models.ManyToManyField('self', verbose_name=_('Guardians / Parents'),
                                        symmetrical=False, related_name='children')