Denormalising users shouldn't call save on edition

www.agileplannerapp.com/boards/173808/cards/4296

Denormalising users is a process that's setting values for a few columns, which doesn't need the the entire validation chain or callbacks to execute. there are no validations related to denormalisation, all the more reason for it to be a plain #set operation.

there's a cost involved here of multiple update queries being fired, but that should be substantially lower than triggering callbacks and validation chain repeatedly.