Issue 351: Reimplement OAuth2 - Step 2 (Auth PCL - only data types)

Src/GoogleApis.Auth/OAuth2/ICodeReceiver.cs

Index: Src/GoogleApis.Auth/OAuth2/ICodeReceiver.cs
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new file mode 100644
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 b/Src/GoogleApis.Auth/OAuth2/ICodeReceiver.cs
@@ -0,0 1,38 @@
 /*
 Copyright 2013 Google Inc
 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.
 */
 using System.Threading;
 using System.Threading.Tasks;
 using Google.Apis.Auth.OAuth2.Requests;
 using Google.Apis.Auth.OAuth2.Responses;
 namespace Google.Apis.Auth.OAuth2
 {
 /// <summary>OAuth 2.0 verification code receiver.</summary>
 public interface ICodeReceiver
 {
 /// <summary>Gets the redirected URI.</summary>
 string RedirectUri { get; }
 /// <summary>Receives the authorization code.</summary>
 /// <param name="url">The authorization code request URL</param>
 /// <param name="taskCancellationToken">Cancellation token</param>
 /// <returns>The authorization code response</returns>
 Task<AuthorizationCodeResponseUrl> ReceiveCodeAsync(AuthorizationCodeRequestUrl url,
 CancellationToken taskCancellationToken);
 }
 }