invoice-ninja: Deploy Invoice Ninja

Invoice Ninja is a small business management tool.  Tabitha wants to
use it for HLC.

I am a bit concerned about the code quality of this application, and
definitely alarmed at the data it send upstream, so I have tried to be
extra careful with it.  All privileges are revoked, including access to
the Internet.

invoice-ninja/namespace.yaml

@@ -0,0 +1,7 @@
+apiVersion: v1
+kind: Namespace
+metadata:
+  name: invoice-ninja
+  labels:
+    app.kubernetes.io/name: invoice-ninja
+    app.kubernetes.io/component: invoice-ninja