anchor.diff:  
   Sometimes an exception might occur in your notification plugin due to which it might not be able to handle the event sent to it by Kill Bill. By default, if a plugin triggers a runtime exception, Kill Bill dispatches the event right away up to 3 times (or as configured by the `org.killbill.notificationq.external.max.failure.retry` global property). However, in some cases, you may want Kill Bill to retry sending the event again at a later time (if for example a third-party provider is down). To do so, your plugin can throw a `NotificationPluginApiRetryException` to include its own retry schedule. The retry schedule should include a Period array, each element in the array should specify the duration after which the retry should be attempted. 
   
  -For example consider the following exception:
  +For example, consider the following exception:
   [source,java]
   // Retry in an hour and in 24hrs
   throw new NotificationPluginApiRetryException(Arrays.asList(new Period[]{Period.hours(1), Period.days(1)}));
  
positive.code: |SUBSCRIPTION_CANCEL
  |Occurs when a subscription is cancelled
  |SUBSCRIPTION_UNCANCEL
  |Occurs when a subscription cancellation is undone (Note that subscription cancellation  cannot be undone once the cancellation becomes effective)
  |SUBSCRIPTION_BCD_CHANGE
  |Occurs when the subscription billing date is changed
  |ENTITLEMENT_CREATION
  
negative.code: |ACCOUNT_CHANGE
  |Occurs when a customer account is modified
  |BLOCKING_STATE
  |Occurs when there is a change in the state of an entitlement or billing. See https://killbill.github.io/slate/#account-blocking-state[Blocking States] to know more
  |BROADCAST_SERVICE
  |Used to broadcast an event to other Kill Bill nodes (Typically used for plugin related events like plugin installation, plugin uninstallation, plugin start, plugin stop, etc.)
  |SUBSCRIPTION_CREATION
  |Occurs when a new subscription is created
  |SUBSCRIPTION_PHASE
  