Move comment user label extraction to the model

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

mayan/apps/document_comments/models.py

@@ -60,6 +60,13 @@ class Comment(models.Model):
             viewname='comments:comment_details', kwargs={'pk': self.pk}
         )
 
+    def get_user_label(self):
+        if self.user.get_full_name():
+            return self.user.get_full_name()
+        else:
+            return self.user.username
+    get_user_label.short_description = _('User')
+
     def save(self, *args, **kwargs):
         _user = kwargs.pop('_user', None) or self.user
         created = not self.pk