Credentials store API (#38)

* CredentialService initial impl with Win32 support

- Basic CredentialService APIs for Save, Read, Delete
- E2E unit tests for Credential Service
- Win32 implementation with unit tests

* Save Password support on Mac v1

- Basic keychain support on Mac using Interop with the KeyChain APIs
- All but 1 unit test passing. This will pass once API is changed, but checking this in with the existing API so that if we decide to alter behavior, we have a reference point.

* Remove Username from Credentials API

- Removed Username option from Credentials as this caused conflicting behavior on Mac vs Windows

* Cleanup Using Statements and add Copyright

* Linux CredentialStore Prototype

* Linux credential store support

- Full support for Linux credential store with tests

* Plumbed CredentialService into Program init

* Addressing Pull Request comments

test/Microsoft.SqlTools.ServiceLayer.Test/Utility/RequestContextMocks.cs

@@ -0,0 +1,77 @@
+//
+// 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.Threading.Tasks;
+using Microsoft.SqlTools.ServiceLayer.Hosting.Protocol;
+using Microsoft.SqlTools.ServiceLayer.Hosting.Protocol.Contracts;
+using Moq;
+
+namespace Microsoft.SqlTools.ServiceLayer.Test.Utility
+{
+    public static class RequestContextMocks
+    {
+
+        public static Mock<RequestContext<TResponse>> Create<TResponse>(Action<TResponse> resultCallback)
+        {
+            var requestContext = new Mock<RequestContext<TResponse>>();
+
+            // Setup the mock for SendResult
+            var sendResultFlow = requestContext
+                .Setup(rc => rc.SendResult(It.IsAny<TResponse>()))
+                .Returns(Task.FromResult(0));
+            if (resultCallback != null)
+            {
+                sendResultFlow.Callback(resultCallback);
+            }
+            return requestContext;
+        }
+
+        public static Mock<RequestContext<TResponse>> AddEventHandling<TResponse, TParams>(
+            this Mock<RequestContext<TResponse>> mock,
+            EventType<TParams> expectedEvent,
+            Action<EventType<TParams>, TParams> eventCallback)
+        {
+            var flow = mock.Setup(rc => rc.SendEvent(
+                It.Is<EventType<TParams>>(m => m == expectedEvent),
+                It.IsAny<TParams>()))
+                .Returns(Task.FromResult(0));
+            if (eventCallback != null)
+            {
+                flow.Callback(eventCallback);
+            }
+
+            return mock;
+        }
+
+        public static Mock<RequestContext<TResponse>> AddErrorHandling<TResponse>(
+            this Mock<RequestContext<TResponse>> mock,
+            Action<object> errorCallback)
+        {
+
+            // Setup the mock for SendError
+            var sendErrorFlow = mock.Setup(rc => rc.SendError(It.IsAny<object>()))
+                .Returns(Task.FromResult(0));
+            if (mock != null && errorCallback != null)
+            {
+                sendErrorFlow.Callback(errorCallback);
+            }
+
+            return mock;
+        }
+
+        public static Mock<RequestContext<TResponse>> SetupRequestContextMock<TResponse, TParams>(
+            Action<TResponse> resultCallback,
+            EventType<TParams> expectedEvent,
+            Action<EventType<TParams>, TParams> eventCallback,
+            Action<object> errorCallback)
+        {
+            return Create(resultCallback)
+                .AddEventHandling(expectedEvent, eventCallback)
+                .AddErrorHandling(errorCallback);            
+        }
+
+    }
+}

test/Microsoft.SqlTools.ServiceLayer.Test/Utility/TestObjects.cs

@@ -6,20 +6,13 @@
 //#define USE_LIVE_CONNECTION
 
 using System;
-using System.Collections;
 using System.Collections.Generic;
 using System.Data;
 using System.Data.Common;
-using System.Data.SqlClient;
-using System.Linq;
-using System.Threading;
-using System.Threading.Tasks;
 using Microsoft.SqlTools.ServiceLayer.Connection;
 using Microsoft.SqlTools.ServiceLayer.Connection.Contracts;
 using Microsoft.SqlTools.ServiceLayer.LanguageServices;
-using Microsoft.SqlTools.ServiceLayer.SqlContext;
 using Microsoft.SqlTools.ServiceLayer.Test.Utility;
-using Xunit;
 
 namespace Microsoft.SqlTools.Test.Utility
 {

test/Microsoft.SqlTools.ServiceLayer.Test/Utility/TestUtils.cs

@@ -0,0 +1,25 @@
+using System;
+using System.Runtime.InteropServices;
+
+namespace Microsoft.SqlTools.ServiceLayer.Test.Utility
+{
+    public static class TestUtils
+    {
+
+        public static void RunIfLinux(Action test)
+        {
+            if (RuntimeInformation.IsOSPlatform(OSPlatform.Linux))
+            {
+                test();
+            }
+        }
+        
+        public static void RunIfWindows(Action test)
+        {
+            if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
+            {
+                test();
+            }
+        }
+    }
+}