Convert the document version list view to item view mode.

Add document version preview and thumbnail widgets.
Update the new version upload event have the version
as the target and the document as the action object.

Backported from the development branch.

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

mayan/apps/documents/models.py

@@ -7,6 +7,7 @@ import uuid
 from django.conf import settings
 from django.core.files import File
 from django.db import models, transaction
+from django.template import Template, Context
 from django.urls import reverse
 from django.utils.encoding import force_text, python_2_unicode_compatible
 from django.utils.timezone import now
@@ -395,7 +396,9 @@ class DocumentVersion(models.Model):
         verbose_name_plural = _('Document version')
 
     def __str__(self):
-        return '{0} - {1}'.format(self.document, self.timestamp)
+        return Template(
+            '{{ instance.document }} - {{ instance.timestamp }}'
+        ).render(context=Context({'instance': self}))
 
     def delete(self, *args, **kwargs):
         for page in self.pages.all():
@@ -405,6 +408,9 @@ class DocumentVersion(models.Model):
 
         return super(DocumentVersion, self).delete(*args, **kwargs)
 
+    def get_absolute_url(self):
+        return reverse('documents:document_version_view', args=(self.pk,))
+
     def save(self, *args, **kwargs):
         """
         Overloaded save method that updates the document version's checksum,
@@ -453,7 +459,7 @@ class DocumentVersion(models.Model):
         else:
             if new_document_version:
                 event_document_new_version.commit(
-                    actor=user, target=self.document
+                    actor=user, target=self, action_object=self.document
                 )
                 post_version_upload.send(sender=DocumentVersion, instance=self)