Allowing updates without first fetching the record

[whitfin]

Following on from https://github.com/nayaverdier/dyntastic/issues/21#issuecomment-2156202427.

I don't really have a clear path to this, but I'd expect something like:

Model.update("id", updates..., refresh=False (or true!))

Maybe it needs a new name beyond update, not sure. I definitely think this would be a great addition though.