cached flavours of Model.save() objects.get() and objects.filter() #5263

[evrenesat]

To ease the development and remove complexity from app logic, we need to handle and compensate ~1 second Riak-Solr sync delay at orm layer. For this purpose, I'm going to implement cached_save(), cached_filter() and cached_get() methods which can be used when developer need to access to just created object within 1s time frame.