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.Hosting.UnitTests/ExtensibilityTests/ServiceProviderTests.cs

@@ -0,0 +1,119 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+using System;
+using System.Linq;
+using Microsoft.SqlTools.Hosting.Extensibility;
+using Microsoft.SqlTools.Hosting.Utility;
+using NUnit.Framework;
+
+namespace Microsoft.SqlTools.Hosting.UnitTests.ExtensibilityTests
+{
+
+    [TestFixture]
+    public class ServiceProviderTests
+    {
+        private RegisteredServiceProvider provider;
+
+        [SetUp]
+        public void SetupServiceProviderTests()
+        {
+            provider = new RegisteredServiceProvider();
+        } 
+
+        [Test]
+        public void GetServiceShouldReturnNullIfNoServicesRegistered()
+        {
+            // Given no service registered
+            // When I call GetService
+            var service = provider.GetService<MyProviderService>();
+            // Then I expect null to be returned
+            Assert.Null(service);
+        }
+
+
+        [Test]
+        public void GetSingleServiceThrowsMultipleServicesRegistered()
+        {
+            // Given 2 services registered
+            provider.Register(() => new[] { new MyProviderService(), new MyProviderService() });
+            // When I call GetService
+            // Then I expect to throw
+            Assert.Throws<InvalidOperationException>(() => provider.GetService<MyProviderService>());
+        }
+
+        [Test]
+        public void GetServicesShouldReturnEmptyIfNoServicesRegistered()
+        {
+            // Given no service regisstered
+            // When I call GetService
+            var services = provider.GetServices<MyProviderService>();
+            Assert.That(services, Is.Empty, "provider.GetServices with no service registered");
+        }
+
+        [Test]
+        public void GetServiceShouldReturnRegisteredService()
+        {
+            MyProviderService service = new MyProviderService();
+            provider.RegisterSingleService(service);
+
+            var returnedService = provider.GetService<MyProviderService>();
+            Assert.AreEqual(service, returnedService);            
+        }
+
+        // DEVNOTE: The name of this test doesn't match the code, which is pretty much the same as the one above.
+        [Test]
+        public void GetServicesShouldReturnRegisteredServiceWhenMultipleServicesRegistered()
+        {
+            MyProviderService service = new MyProviderService();
+            provider.RegisterSingleService(service);
+
+            var returnedServices = provider.GetServices<MyProviderService>();
+            Assert.AreEqual(service, returnedServices.Single());
+        }
+
+        [Test]
+        public void RegisterServiceProviderShouldThrowIfServiceIsIncompatible()
+        {
+            MyProviderService service = new MyProviderService();
+            Assert.Throws<InvalidOperationException>(() => provider.RegisterSingleService(typeof(OtherService), service));
+        }
+        [Test]
+        public void RegisterServiceProviderShouldThrowIfServiceAlreadyRegistered()
+        {
+            MyProviderService service = new MyProviderService();
+            provider.RegisterSingleService(service);
+
+            Assert.Throws<InvalidOperationException>(() => provider.RegisterSingleService(service));
+        }
+        
+        [Test]
+        public void RegisterShouldThrowIfServiceAlreadyRegistered()
+        {
+            MyProviderService service = new MyProviderService();
+            provider.RegisterSingleService(service);
+
+            Assert.Throws<InvalidOperationException>(() => provider.Register(() => service.AsSingleItemEnumerable()));
+        }
+
+        [Test]
+        public void RegisterShouldThrowIfServicesAlreadyRegistered()
+        {
+            provider.Register(() => new [] { new MyProviderService(), new MyProviderService() });
+            Assert.Throws<InvalidOperationException>(() => provider.Register(() => new MyProviderService().AsSingleItemEnumerable()));
+        }
+    }
+
+
+    public class MyProviderService
+    {
+
+    }
+
+    public class OtherService
+    {
+
+    }
+}