Add variation_name, workflow_id, workflow_name to webhooks

We want a higher level view of the affect our experiemnts are having. To be able to analyse this in Amplitude I'd like to be able to create a cohort of users where "email delivered" with property variation_name = control and then compare that to another cohort where email-delivered with property variation_name = A At the moment I'm only seeing variation_id via the Segment webhook integration.