anchor.diff:  
   When retrieving entitlement/overdue status, the web site could be implemented to take all kinds of actions such as displaying warning message, degrading experience, emailing customer, ...
   
  -
   === Custom Plugins
   
   In the previous section, we discussed a possible implementation where the web site queries the billing system to figure out the entitlement story attached to a customer (when he logs-in for instance). Another pattern is to create a custom notification plugin that will listen to `Overdue` events and take appropriate action. The plugin would need to handle the `OVERDUE_CHANGE` event. 
  
positive.code: [start = 15]
  . Move clock +5 day (`2021-09-26`) and observe the final payment retry. Verify that the payment is successful and the account is moved to the `CLEAR` status.
  
  [[platform_use]]
  == Use of the Platform
  
  
negative.code: * Email/Notify user about the new state (We already have a Java  https://github.com/killbill/killbill-email-notifications-plugin[email notification plugin] which can be extended to handle `OVERDUE_CHANGE` events)
  * Take action to modify the experience (based on the state name): for instance to degrade the service, modify the login flow to prompt for payment, ...
  
  
  == Additional Resources
  
  