Add Schema Compare (#777)

* successfully sends list of differences to ADS

* bumping dacfx nuget package version

* add second schema compare try for case when first db to db comparison fails but works on second try

* move schemacompare out of dacfx folders

* capitalizing

* more capitalizing

* addressing comments

src/Microsoft.SqlTools.ServiceLayer/SchemaCompare/Contracts/SchemaCompareRequest.cs

@@ -0,0 +1,96 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+using Microsoft.SqlServer.Dac.Compare;
+using Microsoft.SqlTools.Hosting.Protocol.Contracts;
+using Microsoft.SqlTools.ServiceLayer.TaskServices;
+using Microsoft.SqlTools.ServiceLayer.Utility;
+using System.Collections.Generic;
+
+namespace Microsoft.SqlTools.ServiceLayer.SchemaCompare.Contracts
+{
+    public enum SchemaCompareEndpointType
+    {
+        Database,
+        Dacpac
+    }
+
+    public class SchemaCompareEndpointInfo
+    {
+        /// <summary>
+        /// Gets or sets the type of the endpoint
+        /// </summary>
+        public SchemaCompareEndpointType EndpointType { get; set; }
+
+        /// <summary>
+        /// Gets or sets package filepath
+        /// </summary>
+        public string PackageFilePath { get; set; }
+
+        /// <summary>
+        /// Gets or sets name for the database
+        /// </summary>
+        public string DatabaseName { get; set; }
+
+        /// <summary>
+        /// Connection uri
+        /// </summary>
+        public string OwnerUri { get; set; }
+    }
+
+    /// <summary>
+    /// Parameters for a schema compare request.
+    /// </summary>
+    public class SchemaCompareParams
+    {
+        /// <summary>
+        /// Gets or sets the source endpoint info
+        /// </summary>
+        public SchemaCompareEndpointInfo SourceEndpointInfo { get; set; }
+
+        /// <summary>
+        /// Gets or sets the target endpoint info
+        /// </summary>
+        public SchemaCompareEndpointInfo TargetEndpointInfo { get; set; }
+
+        /// <summary>
+        /// Executation mode for the operation. Default is execution
+        /// </summary>
+        public TaskExecutionMode TaskExecutionMode { get; set; }
+    }
+
+    /// <summary>
+    /// Parameters returned from a schema compare request.
+    /// </summary>
+    public class SchemaCompareResult : ResultStatus
+    {
+        public string OperationId { get; set; }
+
+        public bool AreEqual { get; set; }
+
+        public List<DiffEntry> Differences { get; set; }
+    }
+
+    public class DiffEntry
+    {
+        public SchemaUpdateAction UpdateAction;
+        public SchemaDifferenceType DifferenceType;
+        public string Name;
+        public string SourceValue;
+        public string TargetValue;
+        public DiffEntry Parent;
+        public List<DiffEntry> Children;
+        public string SourceScript;
+        public string TargetScript;
+    }
+
+    /// <summary>
+    /// Defines the Schema Compare request type
+    /// </summary>
+    class SchemaCompareRequest
+    {
+        public static readonly RequestType<SchemaCompareParams, SchemaCompareResult> Type =
+            RequestType<SchemaCompareParams, SchemaCompareResult>.Create("schemaCompare/compare");
+    }
+}