allow missing SSO usernames (anon user)

users/migrations/0009_alter_user_sso_username.py

+# Generated by Django 4.1.4 on 2023-05-25 22:57
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('users', '0008_alter_user_rsvp_lectures'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='user',
+            name='sso_username',
+            field=models.CharField(blank=True, max_length=128, null=True, verbose_name='Username z SSO'),
+        ),
+    ]

users/models.py

@@ -19,6 +19,8 @@ class Group:
 class User(pirates_models.AbstractUser):
     sso_username = models.CharField(
         max_length=128,
+        blank=True,
+        null=True,
         verbose_name="Username z SSO",
     )