Create a script that can validate models that have orphaned projects

ZD: https://gitlab.zendesk.com/agent/tickets/62319

Due to some errant project deletion issues, there are some models that have orphaned projects (e.g. project ID doesn't exist in the DB). We should have a script/Rake task a script that can walk through the different models and identify which objects are orphaned. We may start as a separate snippet for this, but I suspect this script may provide insights into what is properly deleted and what is not.

/cc: @dblessing