Integrate generate script with task service (#426)

* Support generate script for backup

* change

* update task service data contract for Generate Script

* more changes

* update test

* add comments

* Add missing files

* update stub backup operation for testing

* pr comments

* remove empty space

* Fix tests

* Add unit/integration tests and isCancelable to TaskInfo

* address pr comments

* pr comments - fix tests

* fix minor issue

* fix minor issues

* remove unused variable

src/Microsoft.SqlTools.ServiceLayer/DisasterRecovery/BackupOperation/IBackupOperation.cs

@@ -0,0 +1,38 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+using Microsoft.SqlServer.Management.Smo;
+using Microsoft.SqlTools.ServiceLayer.Admin;
+using Microsoft.SqlTools.ServiceLayer.DisasterRecovery.Contracts;
+using Microsoft.SqlTools.ServiceLayer.TaskServices;
+using System.Data.SqlClient;
+
+namespace Microsoft.SqlTools.ServiceLayer.DisasterRecovery
+{
+    /// <summary>
+    /// Interface for backup operations
+    /// </summary>
+    public interface IBackupOperation: IScriptableTaskOperation
+    {
+        /// <summary>
+        /// Initialize 
+        /// </summary>
+        /// <param name="dataContainer"></param>
+        /// <param name="sqlConnection"></param>
+        void Initialize(CDataContainer dataContainer, SqlConnection sqlConnection);
+
+        /// <summary>
+        /// Return database metadata for backup
+        /// </summary>
+        /// <param name="databaseName"></param>
+        /// <returns></returns>
+        BackupConfigInfo CreateBackupConfigInfo(string databaseName);
+
+        /// <summary>
+        /// Set backup input properties
+        /// </summary>
+        /// <param name="input"></param>
+        void SetBackupInput(BackupInfo input);
+    }
+}