Replace deprecated GoogleCredential with new auth lib (#129)

Replace deprecated GoogleCredential with new lib

This PR also introduced a CredentialsBundle class to carry
HttpTransport and JsonFactory object which are needed by
most of the GCP library to instantiate client.

util/src/main/java/google/registry/util/GoogleCredentialsBundle.java

@@ -0,0 +1,70 @@
+// Copyright 2019 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.util;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+
+import com.google.api.client.googleapis.util.Utils;
+import com.google.api.client.http.HttpRequestInitializer;
+import com.google.api.client.http.HttpTransport;
+import com.google.api.client.json.JsonFactory;
+import com.google.auth.http.HttpCredentialsAdapter;
+import com.google.auth.oauth2.GoogleCredentials;
+
+/**
+ * Helper class to provide {@link HttpTransport}, {@link JsonFactory} and {@link
+ * HttpRequestInitializer} for a given {@link GoogleCredentials}. These classes are normally needed
+ * for creating the instance of a GCP client.
+ */
+public class GoogleCredentialsBundle {
+
+  private GoogleCredentials googleCredentials;
+  private HttpTransport httpTransport;
+  private JsonFactory jsonFactory;
+  private HttpRequestInitializer httpRequestInitializer;
+
+  private GoogleCredentialsBundle(GoogleCredentials googleCredentials) {
+    checkNotNull(googleCredentials);
+    this.googleCredentials = googleCredentials;
+    this.httpTransport = Utils.getDefaultTransport();
+    this.jsonFactory = Utils.getDefaultJsonFactory();
+    this.httpRequestInitializer = new HttpCredentialsAdapter(googleCredentials);
+  }
+
+  /** Creates a {@link GoogleCredentialsBundle} instance from given {@link GoogleCredentials}. */
+  public static GoogleCredentialsBundle create(GoogleCredentials credentials) {
+    return new GoogleCredentialsBundle(credentials);
+  }
+
+  /** Returns the same {@link GoogleCredentials} used to create this object. */
+  public GoogleCredentials getGoogleCredentials() {
+    return googleCredentials;
+  }
+
+  /** Returns the instance of {@link HttpTransport}. */
+  public HttpTransport getHttpTransport() {
+    return httpTransport;
+  }
+
+  /** Returns the instance of {@link JsonFactory}. */
+  public JsonFactory getJsonFactory() {
+    return jsonFactory;
+  }
+
+  /** Returns the instance of {@link HttpRequestInitializer}. */
+  public HttpRequestInitializer getHttpRequestInitializer() {
+    return httpRequestInitializer;
+  }
+}