Implement login/logout commands

Refactor the auth code into its own dagger module, add tests and use the new interfaces to implement the login and logout commands.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=149108266

java/google/registry/tools/LogoutCommand.java

@@ -0,0 +1,36 @@
+// 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.tools;
+
+import com.google.api.client.auth.oauth2.StoredCredential;
+import com.google.api.client.util.store.AbstractDataStoreFactory;
+import google.registry.util.FormattingLogger;
+import java.io.IOException;
+import javax.inject.Inject;
+
+/** Logout (invalidates OAuth credentials). */
+class LogoutCommand implements Command {
+
+  private static final FormattingLogger logger = FormattingLogger.getLoggerForCallerClass();
+
+  @Inject AbstractDataStoreFactory dataStoreFactory;
+  @Inject @AuthModule.ClientScopeQualifier String clientScopeQualifier;
+
+  @Override
+  public void run() throws IOException {
+    StoredCredential.getDefaultDataStore(dataStoreFactory).clear();
+    logger.infofmt("Logged out - credentials have been removed.");
+  }
+}