Initial commit adding document checkout support

apps/checkouts/managers.py

@@ -0,0 +1,26 @@
+from __future__ import absolute_import
+
+from django.db import models
+
+from documents.models import Document
+
+from .exceptions import DocumentNotCheckedOut
+
+
+class DocumentCheckoutManager(models.Manager):
+    def checked_out(self):
+        return Document.objects.filter(pk__in=self.model.objects.all().values_list('pk', flat=True))
+
+    def is_document_checked_out(self, document):
+        if self.model.objects.filter(document=document):
+            return True
+        else:
+            return False
+            
+    def check_in_document(self, document):
+        try:
+            document_checkout = self.model.objects.get(document=document)
+        except self.model.DoesNotExist:
+            raise DocumentNotCheckedOut
+        else:
+            document_checkout.delete()