anchor.diff:  
   Missing Usage Data:
   
  -Currently it is considered an error to delete past usage data in these past 2 periods, the invoicing system would throw an error and prevent invoicing to happen correctly. If the late missing data is older than these past 2 periods, it is simply ignored.
  +Currently it is considered an error to delete past usage data in these past 2 periods. IF this occurs, the invoicing system throws an error and prevents invoicing from happening correctly. If the late missing data is older than these past 2 periods, it is simply ignored.
   
   One can set the system property -- or per-tenant config -- `org.killbill.invoice.readMaxRawUsagePreviousPeriod` to `0` to ignore any past data -- late usage or missing data.
   
  
positive.code: ==== Usage Invoice Items
  
  As described in the section http://docs.killbill.io/latest/userguide_subscription.html#components-catalog-usage[Usage Billing],
  Kill Bill supports invoicing customers based on different usage type. The usage billing is always done on a per subscription
  level and for a given billing period; in addition, if the active `Plan` associated with the subscription contains multiple usage
  sections, each usage section is billed independently: As a result, we may see one or several `USAGE` invoice items per invoice,
  each associated with a given subscription, usage section and billing period.
  
  Regarless of the usage type the following basic fields will always be seen:
  
  * `planName`: The name of the `Plan` in the catalog
  * `phaseName`: The name of the `PlanPhase` in the catalog
  
negative.code: * `endDate`: The end date for the period being invoiced
  
  In addition, depending on the usage type for the usage section (e.g `CONSUMABLE`), and depending on the configuration of the system,
  we may see additional information. 
  
  ==== Capacity In Arrear Mode
  
  This mode bills based on actual usage, using a fixed price for the highest tier reached. For each capacity in arrear usage section, we will see some json in the field `itemDetails`, to provide additional information:
  
  [source,bash]
  ----
  