Add apache beam to registry and open source

This is the initial commit of the new billing system, rewritten as an Apache
Beam pipeline. This contains a basic end-to-end pipeline as proof of concept,
and boilerplate for GenerateInvoicesAction, which will eventually be our
automated invoice generation endpoint.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=174184171

java/google/registry/billing/MinWordCount.java

@@ -0,0 +1,42 @@
+// Copyright 2017 The Nomulus Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package google.registry.billing;
+
+import org.apache.beam.sdk.transforms.DoFn;
+
+/** A minimal word count, serving as proof of concept for the Beam pipeline. */
+public class MinWordCount implements Runnable {
+
+  public static void main(String[] args) {
+    MinWordCount wordCount = new MinWordCount();
+    wordCount.run();
+  }
+
+  @Override
+  public void run() {
+    // This is a stub function for a basic proof-of-concept Beam pipeline.
+  }
+
+  static class ExtractWordsFn extends DoFn<String, String> {
+    @ProcessElement
+    public void processElement(ProcessContext c) {
+      for (String word : c.element().split("[^\\p{L}]+")) {
+        if (!word.isEmpty()) {
+          c.output(word);
+        }
+      }
+    }
+  }
+}