Style: Move document model functions

Move the document UUID and document hash functions
to the documents.utils module.

Signed-off-by: Roberto Rosario <Roberto.Rosario@mayan-edms.com>

mayan/apps/documents/utils.py

@@ -1,6 +1,10 @@
 from __future__ import unicode_literals
 
+import hashlib
+import uuid
+
 from django.apps import apps
+from django.utils.encoding import force_text
 
 from .literals import DOCUMENT_IMAGES_CACHE_NAME
 
@@ -12,6 +16,14 @@ def callback_update_cache_size(setting):
     cache.save()
 
 
+def document_hash_function(data):
+    return hashlib.sha256(data).hexdigest()
+
+
+def document_uuid_function(*args, **kwargs):
+    return force_text(uuid.uuid4())
+
+
 def parse_range(astr):
     # http://stackoverflow.com/questions/4248399/
     # page-range-for-printing-algorithm