Improve natural key handing for the Document, Metadata, DocumentMetadata, DocumentTypeOCRSetting and UserProfileLocale models.

Signed-off-by: Roberto Rosario <roberto.rosario.gonzalez@gmail.com>

mayan/apps/common/managers.py

@@ -1,6 +1,7 @@
 from __future__ import unicode_literals
 
 from django.apps import apps
+from django.contrib.auth import get_user_model
 from django.contrib.contenttypes.fields import GenericRelation
 from django.db import models
 
@@ -11,3 +12,14 @@ class ErrorLogEntryManager(models.Manager):
             app_label='common', model_name='ErrorLogEntry'
         )
         model.add_to_class('error_logs', GenericRelation(ErrorLogEntry))
+
+
+class UserLocaleProfileManager(models.Manager):
+    def get_by_natural_key(self, user_natural_key):
+        User = get_user_model()
+        try:
+            user = User.objects.get_by_natural_key(user_natural_key)
+        except User.DoesNotExist:
+            raise self.model.DoesNotExist
+
+        return self.get(user__pk=user.pk)