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/Contracts/BackupRequest.cs

@@ -7,13 +7,30 @@ using Microsoft.SqlTools.Hosting.Protocol.Contracts;
 
 namespace Microsoft.SqlTools.ServiceLayer.DisasterRecovery.Contracts
 {
+    /// <summary>
+    /// Backup parameters passed for execution and scripting
+    /// </summary>
     public class BackupParams
     {
+        /// <summary>
+        /// Connection uri
+        /// </summary>
         public string OwnerUri { get; set; }
 
+        /// <summary>
+        /// Backup metrics selected from the UI
+        /// </summary>
         public BackupInfo BackupInfo { get; set; }
+
+        /// <summary>
+        /// True for generating script, false for execution
+        /// </summary>
+        public bool IsScripting { get; set; }
     }
 
+    /// <summary>
+    /// Response class for backup execution
+    /// </summary>
     public class BackupResponse
     {
         public bool Result { get; set; }
@@ -21,6 +38,9 @@ namespace Microsoft.SqlTools.ServiceLayer.DisasterRecovery.Contracts
         public int TaskId { get; set; }
     }
 
+    /// <summary>
+    /// Request class for backup execution
+    /// </summary>
     public class BackupRequest
     {
         public static readonly