Merge pull request #124 from vshn/add/billing-test-ns

Add note about testing namespace and billing

docs/modules/ROOT/pages/reference/vshn-usage-reporting.adoc

@@ -89,4 +89,10 @@ NOTE: Some links may require permissions and might not be accessible if you lack
 
 === Data Model and Flow
 
-See the https://docs.central.vshn.ch/metered-billing-data-flow.html[Data Model and Flow] for a generic overview of the data flow for Odoo.
+See the https://docs.central.vshn.ch/metered-billing-data-flow.html[Data Model and Flow] for a generic overview of the data flow for Odoo.
+
+== Special testing namespace
+
+On each APPUiO cluster there's a special testing namespace that will not create any usage reporting.
+
+It's usually `vshn-test`, it's defined in `appcat.billing.ignoreNamespace` in the component-appcat.