Sync registrar to Braintree customer record automatically

In order to set the customerId field on a payment, the customer entry
must exist in Braintree's database. This CL causes it to be created or
updated before processing the payment.
-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=118530040

javatests/com/google/domain/registry/testing/ReflectiveFieldExtractor.java

@@ -0,0 +1,37 @@
+// Copyright 2016 The Domain Registry 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 com.google.domain.registry.testing;
+
+import static com.google.common.base.Preconditions.checkArgument;
+
+import java.lang.reflect.Field;
+
+/** Utility class for extracting encapsulated contents of objects for testing. */
+public final class ReflectiveFieldExtractor {
+
+  /** Extracts private {@code fieldName} on {@code object} without public getter. */
+  public static <T> T extractField(Class<T> returnType, Object object, String fieldName)
+      throws NoSuchFieldException, SecurityException, IllegalAccessException {
+    Field field = object.getClass().getDeclaredField(fieldName);
+    field.setAccessible(true);
+    Object value = field.get(object);
+    checkArgument(value == null || returnType.isInstance(value));
+    @SuppressWarnings("unchecked")
+    T result = (T) value;
+    return result;
+  }
+
+  private ReflectiveFieldExtractor() {}
+}