title: Intercepting Campaign Product List Changes
body: <p>I've been looking for a way to keep in sync two campaign product lists. I haven't found a message to intercept when a product is added to or removed from a campaign list.</p>
  
  <p>CampaignItem, the intersect entity used for the N:N campaign-product relationship (among others), cannot be used as a target of a plugin step.</p>
  
  <p>What are my options here?</p>
  
  <p>Thanks.</p>