Items must have a uid now (not null).

This is due to the previous change.

django_etebase/migrations/0017_auto_20200623_0958.py

@@ -0,0 +1,25 @@
+# Generated by Django 3.0.3 on 2020-06-23 09:58
+
+import django.core.validators
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('django_etebase', '0016_auto_20200623_0820'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='collection',
+            name='main_item',
+            field=models.ForeignKey(null=True, on_delete=django.db.models.deletion.SET_NULL, related_name='parent', to='django_etebase.CollectionItem'),
+        ),
+        migrations.AlterField(
+            model_name='collectionitem',
+            name='uid',
+            field=models.CharField(db_index=True, max_length=43, validators=[django.core.validators.RegexValidator(message='Not a valid UID', regex='^[a-zA-Z0-9]*$')]),
+        ),
+    ]