BUG Don't instanciate ALL recipients in enqueue() just for their ID
BUG Don't instanciate ALL recipients in enqueue() just for their ID

This set might contain thousands of records, we really don't
want them as in-memory objects.

silverstripe-archive/silverstripe-newsletter,guru-digital/silverstripe-newsletter,silverstripe-labs/silverstripe-newsletter,guru-digital/silverstripe-newsletter,silverstripe-labs/silverstripe-newsletter,silverstripe-archive/silverstripe-newsletter,guru-digital/silverstripe-newsletter,silverstripe-labs/silverstripe-newsletter