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/ServiceHostTests/ExtensibleServiceHostTest.cs

@@ -0,0 +1,80 @@
+//
+// 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 Microsoft.SqlTools.Hosting.Channels;
+using Microsoft.SqlTools.Hosting.Extensibility;
+using Microsoft.SqlTools.Hosting.Protocol;
+using Moq;
+using NUnit.Framework;
+
+namespace Microsoft.SqlTools.Hosting.UnitTests.ServiceHostTests
+{
+    [TestFixture]
+    public class ExtensibleServiceHostTest
+    {
+        [Test]
+        public void CreateExtensibleHostNullProvider()
+        {
+            // If: I create an extensible host with a null provider
+            // Then: I should get an exception
+            var cb = new Mock<ChannelBase>();
+            Assert.Throws<ArgumentNullException>(() => new ExtensibleServiceHost(null, cb.Object));
+        }
+        
+        [Test]
+        public void CreateExtensibleHost()
+        {
+            // Setup: 
+            // ... Create a mock hosted service that can initialize
+            var hs = new Mock<IHostedService>();
+            var mockType = typeof(Mock<IHostedService>);
+            hs.Setup(o => o.InitializeService(It.IsAny<IServiceHost>()));
+            hs.SetupGet(o => o.ServiceType).Returns(mockType);
+            
+            // ... Create a service provider mock that will return some stuff
+            var sp = new Mock<RegisteredServiceProvider>();
+            sp.Setup(o => o.GetServices<IHostedService>())
+                .Returns(new[] {hs.Object});
+            sp.Setup(o => o.RegisterSingleService(mockType, hs.Object));
+            
+            // If: I create an extensible host with a custom provider
+            var cb = new Mock<ChannelBase>();
+            var esh = new ExtensibleServiceHost(sp.Object, cb.Object);
+            
+            // Then:
+           
+            // ... The service should have been initialized
+            hs.Verify(o => o.InitializeService(esh), Times.Once());            
+            // ... The service host should have it's provider exposed
+            Assert.AreEqual(sp.Object, esh.ServiceProvider);
+        }
+
+        [Test]
+        public void CreateDefaultExtensibleHostNullAssemblyList()
+        {
+            // If: I create a default server extensible host with a null provider
+            // Then: I should get an exception
+            var cb = new Mock<ChannelBase>();
+            Assert.Throws<ArgumentNullException>(() => ExtensibleServiceHost.CreateDefaultExtensibleServer(".", null));
+        }
+        
+        [Test]
+        public void CreateDefaultExtensibleHost()
+        {
+            // If: I create a default server extensible host
+            var esh = ExtensibleServiceHost.CreateDefaultExtensibleServer(".", new string[] { });
+            
+            // Then: 
+            // ... The service provider should be setup
+            Assert.NotNull(esh.ServiceProvider);
+            
+            var jh = esh.jsonRpcHost as JsonRpcHost;
+            Assert.NotNull(jh);
+            Assert.That(jh.protocolChannel, Is.InstanceOf<StdioServerChannel>(), "The underlying rpc host should be using the stdio server channel ");
+            Assert.False(jh.protocolChannel.IsConnected);
+        }
+    }
+}