Add User service.

service/user/user.go

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package user
+
+import "google.golang.org/appengine/user"
+
+// User is a mimic of https://godoc.org/google.golang.org/appengine/user#User
+//
+// It's provided here for convenience, and is compile-time checked to be
+// identical.
+type User struct {
+        Email             string
+        AuthDomain        string
+        Admin             bool
+        ID                string
+        ClientID          string
+        FederatedIdentity string
+        FederatedProvider string
+}
+
+var _ User = (User)(user.User{})