bgpwtf/invoice: add recurrent billing tool

Change-Id: Ic3cc03d7b04304ae8c7aa76d8bb889ae8c144838
diff --git a/bgpwtf/invoice/proto/BUILD.bazel b/bgpwtf/invoice/proto/BUILD.bazel
index 2eeae64..a1a7033 100644
--- a/bgpwtf/invoice/proto/BUILD.bazel
+++ b/bgpwtf/invoice/proto/BUILD.bazel
@@ -4,7 +4,10 @@
 
 proto_library(
     name = "proto_proto",
-    srcs = ["invoice.proto"],
+    srcs = [
+        "invoice.proto",
+        "recurrent.proto",
+    ],
     visibility = ["//visibility:public"],
 )