Add parent back to categories

nummi/main/models.py

@@ -6,6 +6,7 @@ from django.forms import ModelForm
 class Category(models.Model):
     id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
     name = models.CharField(max_length=64)
+    parent = models.ForeignKey("self", on_delete=models.SET_NULL, blank=True, null=True)
 
     def __str__(self):
         return self.name