models: drop non-nullity constraint ou API clients' OU (#72703)

src/authentic2/migrations/0045_auto_20221222_1013.py

@@ -0,0 +1,28 @@
+# Generated by Django 2.2.26 on 2022-12-22 09:13
+
+import django.db.models.deletion
+from django.db import migrations, models
+
+import authentic2.a2_rbac.utils
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('authentic2', '0044_apiclient_ou'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='apiclient',
+            name='ou',
+            field=models.ForeignKey(
+                blank=True,
+                default=authentic2.a2_rbac.utils.get_default_ou_pk,
+                null=True,
+                on_delete=django.db.models.deletion.CASCADE,
+                to='a2_rbac.OrganizationalUnit',
+                verbose_name='organizational unit',
+            ),
+        ),
+    ]

src/authentic2/models.py

@@ -727,6 +727,8 @@ class APIClient(models.Model):
         swappable=False,
         on_delete=models.CASCADE,
         default=get_default_ou_pk,
+        null=True,
+        blank=True,
     )
 
     class Meta: