3520 workbench add output association to referential suite
Created by: teddywing
Add an output field to Workbench that associates it with a ReferentialSuite. This new field is required, so there's a callback in place that will create one by default when creating a Workbench if none is specified.
After this, all Workbenches must have an associated ReferentialSuite.
A data migration is included to give existing Workbenches a ReferentialSuite to make them valid under the new requirements.