Add natural key serialization.

mayan/apps/permissions/managers.py

@@ -8,7 +8,15 @@ from django.contrib.contenttypes.models import ContentType
 logger = logging.getLogger(__name__)
 
 
+class RoleManager(models.Manager):
+    def get_by_natural_key(self, label):
+        return self.get(label=label)
+
+
 class StoredPermissionManager(models.Manager):
+    def get_by_natural_key(self, namespace, name):
+        return self.get(namespace=namespace, name=name)
+
     def get_for_holder(self, holder):
         ct = ContentType.objects.get_for_model(holder)
         return self.model.objects.filter(