anchor.diff:  |SUBSCRIPTION_CANCEL
   |Occurs when a subscription is cancelled
   |SUBSCRIPTION_UNCANCEL
  -|Occurs when a cancelled subscription is uncancelled (Note that subscription uncancellation  cannot be done once the cancellation becomes effective )
  +|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
  
positive.code: |ACCOUNT_CHANGE
  |Occurs when a customer account is modified
  |BLOCKING_STATE
  |Occurs when there is a change in state of an entitlement (It becomes BLOCKED or UNBLOCKED)
  |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
  
negative.code: |CUSTOM_FIELD_DELETION
  |Occurs when a custom field is deleted
  |TENANT_CONFIG_CHANGE
  |Occurs when a Tenant configuration is modified (So, any changes to a catalog, overdue config, etc. within a tenant triggers this event)
  |TENANT_CONFIG_DELETION
  |Occurs when a Tenant configuration is deleted
  |===
  