Refactor DnsWriter into the model package

This is one of several CLs in order to support per-TLD DnsWriter
implementations, modeled on the work done for PremiumPricingEngine.

Since DnsWriters will be set inside the Registry object, the DnsWriter
interface definition needs to be moved to models to create minimal
dependency on the rest of the registry codebase to avoid cyclic
dependency.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=128711643

java/google/registry/dns/writer/VoidDnsWriterModule.java

@@ -0,0 +1,29 @@
+// 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 google.registry.dns.writer;
+
+import dagger.Module;
+import dagger.Provides;
+import google.registry.model.dns.DnsWriter;
+
+/** Dagger module that disables DNS updates. */
+@Module
+public final class VoidDnsWriterModule {
+
+  @Provides
+  static DnsWriter provideDnsWriter() {
+    return new VoidDnsWriter();
+  }
+}