Move unused forked code to external directory (#1192)

* Move unused forked code to external directory

* Fix SLN build errors

* Add back resource provider core since it's referenced by main resource provider project

* Update PackageProjects step of pipeline

external/Microsoft.SqlTools.DataProtocol.Contracts/Explorer/CloseSessionRequest.cs

@@ -0,0 +1,53 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+using Microsoft.SqlTools.Hosting.Contracts;
+using Microsoft.SqlTools.DataProtocol.Contracts.Connection;
+
+namespace Microsoft.SqlTools.DataProtocol.Contracts.Explorer
+{
+    /// <summary>
+    /// Information returned from a <see cref="CloseSessionRequest"/>.
+    /// Contains success information, a <see cref="SessionId"/> to be used when
+    /// requesting closing an existing session.
+    /// </summary>
+    public class CloseSessionResponse
+    {
+        /// <summary>
+        /// Boolean indicating if the session was closed successfully 
+        /// </summary>
+        public bool Success { get; set; }
+
+        /// <summary>
+        /// Unique ID to use when sending any requests for objects in the
+        /// tree under the node
+        /// </summary>
+        public string SessionId { get; set; }
+    }
+
+    /// <summary>
+    /// Parameters to the <see cref="CloseSessionRequest"/>.
+    /// </summary>
+    public class CloseSessionParams
+    {
+        /// <summary>
+        /// The Id returned from a <see cref="CreateSessionRequest"/>. This
+        /// is used to disambiguate between different trees. 
+        /// </summary>
+        public string SessionId { get; set; }
+    }
+
+    /// <summary>
+    /// Establishes an Object Explorer tree session for a specific connection.
+    /// This will create a connection to a specific server or database, register
+    /// it for use in the 
+    /// </summary>
+    public class CloseSessionRequest
+    {
+        public static readonly
+            RequestType<CloseSessionParams, CloseSessionResponse> Type =
+            RequestType<CloseSessionParams, CloseSessionResponse>.Create("explorer/closesession");
+    }
+}