added change database handler (#505)

src/Microsoft.SqlTools.ServiceLayer/Connection/Contracts/ChangeDatabaseParams.cs

@@ -0,0 +1,23 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+namespace Microsoft.SqlTools.ServiceLayer.Connection.Contracts
+{
+    /// <summary>
+    /// Parameters for the List Databases Request.
+    /// </summary>
+    public class ChangeDatabaseParams
+    {
+        /// <summary>
+        /// URI of the owner of the connection requesting the list of databases.
+        /// </summary>
+        public string OwnerUri { get; set; }
+
+        /// <summary>
+        /// The database to change to
+        /// </summary>
+        public string NewDatabase { get; set; }
+    }
+}