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.v2/Extensibility/RegisteredServiceProvider.cs

@@ -0,0 +1,121 @@
+//
+// 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.Collections;
+using System.Collections.Generic;
+using System.Globalization;
+using System.Linq;
+using Microsoft.SqlTools.Hosting.Utility;
+using Microsoft.SqlTools.Hosting.v2;
+
+namespace Microsoft.SqlTools.Hosting.Extensibility
+{
+
+    /// <summary>
+    /// A service provider implementation that allows registering of specific services
+    /// </summary>
+    public class RegisteredServiceProvider : ServiceProviderBase
+    {
+        public delegate IEnumerable ServiceLookup();
+
+        protected readonly Dictionary<Type, ServiceLookup> services = new Dictionary<Type, ServiceLookup>();
+
+        /// <summary>
+        /// Registers a singular service to be returned during lookup
+        /// </summary>
+        /// <typeparam name="T"></typeparam>
+        /// <returns>this provider, to simplify fluent declarations</returns>
+        /// <exception cref="ArgumentNullException">If service is null</exception>
+        /// <exception cref="InvalidOperationException">If an existing service is already registered</exception>
+        public virtual RegisteredServiceProvider RegisterSingleService<T>(T service)
+        {
+            Validate.IsNotNull(nameof(service), service);
+            ThrowIfAlreadyRegistered<T>();
+            services.Add(typeof(T), () => service.AsSingleItemEnumerable());
+            return this;
+        }
+
+        /// <summary>
+        /// Registers a singular service to be returned during lookup
+        /// </summary>
+        /// <param name="type">
+        /// Type or interface this service should be registed as. Any <see cref="IMultiServiceProvider.GetServices{T}"/> request
+        /// for that type will return this service
+        /// </param>
+        /// <param name="service">service object to be added</param>
+        /// <returns>this provider, to simplify fluent declarations</returns>
+        /// <exception cref="ArgumentNullException">If service is null</exception>
+        /// <exception cref="InvalidOperationException">If an existing service is already registered</exception>
+        public virtual RegisteredServiceProvider RegisterSingleService(Type type, object service)
+        {
+            Validate.IsNotNull(nameof(type), type);
+            Validate.IsNotNull(nameof(service), service);
+            ThrowIfAlreadyRegistered(type);
+            ThrowIfIncompatible(type, service);
+            services.Add(type, service.AsSingleItemEnumerable);
+            return this;
+        }
+
+        /// <summary>
+        /// Registers a function that can look up multiple services
+        /// </summary>
+        /// <typeparam name="T"></typeparam>
+        /// <returns>this provider, to simplify fluent declarations</returns>
+        /// <exception cref="ArgumentNullException">If <paramref name="serviceLookup"/> is null</exception>
+        /// <exception cref="InvalidOperationException">If an existing service is already registered</exception>
+        public virtual RegisteredServiceProvider Register<T>(Func<IEnumerable<T>> serviceLookup)
+        {
+            Validate.IsNotNull(nameof(serviceLookup), serviceLookup);
+            ThrowIfAlreadyRegistered<T>();
+            services.Add(typeof(T), () => serviceLookup());
+            return this;
+        }
+
+        public virtual void RegisterHostedServices()
+        {
+            // Register all hosted services the service provider for their requested service type.
+            // This ensures that when searching for the ConnectionService (eg) you can get it
+            // without searching for an IHosted service of type ConnectionService
+            foreach (IHostedService service in GetServices<IHostedService>())
+            {
+                RegisterSingleService(service.ServiceType, service);
+            }
+        }
+        
+        private void ThrowIfAlreadyRegistered<T>()
+        {
+            ThrowIfAlreadyRegistered(typeof(T));
+        }
+
+        private void ThrowIfAlreadyRegistered(Type type)
+        {
+            if (services.ContainsKey(type))
+            {
+                throw new InvalidOperationException(string.Format(CultureInfo.CurrentCulture, SR.ServiceAlreadyRegistered, type.Name));
+            }
+
+        }
+
+        private void ThrowIfIncompatible(Type type, object service)
+        {
+            if (!type.IsInstanceOfType(service))
+            {
+                throw new InvalidOperationException(string.Format(CultureInfo.CurrentCulture, SR.ServiceNotOfExpectedType, service.GetType().Name, type.Name));
+            }
+
+        }
+
+        protected override IEnumerable<T> GetServicesImpl<T>()
+        {
+            ServiceLookup serviceLookup;
+            if (services.TryGetValue(typeof(T), out serviceLookup))
+            {
+                return serviceLookup().Cast<T>();
+            }
+            return Enumerable.Empty<T>();
+        }
+    }
+}