Agent Proxy and Credential request handlers (#637)

* Agent Proxy account WIP

* Fixup Credential create\update\delete handlers

* Use current user for test credential

* Cleanup and delete code

* Convert tabs to spaces

src/Microsoft.SqlTools.ServiceLayer/Security/CredentialActions.cs

@@ -0,0 +1,78 @@
+//
+// 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.ServiceLayer.Management;
+using Microsoft.SqlTools.ServiceLayer.Security.Contracts;
+
+namespace  Microsoft.SqlTools.ServiceLayer.Security
+{
+    internal class CredentialActions : ManagementActionBase
+    {
+
+#region Constants
+        private const int MAX_SQL_SYS_NAME_LENGTH = 128; // max sql sys name length
+#endregion
+
+#region Variables
+        private CredentialData credentialData = null;
+        private CredentialInfo credential;
+        private ConfigAction configAction;
+#endregion
+
+#region Constructors / Dispose
+        /// <summary>
+        /// required when loading from Object Explorer context
+        /// </summary>
+        /// <param name="context"></param>
+        public CredentialActions(
+            CDataContainer context,
+            CredentialInfo credential,
+            ConfigAction configAction)
+        {
+            this.DataContainer = context;
+            this.credential = credential;
+            this.configAction = configAction;
+
+            this.credentialData = new CredentialData(context, credential);
+            this.credentialData.Initialize();
+        }
+
+        /// <summary> 
+        /// Clean up any resources being used.
+        /// </summary>
+        protected override void Dispose( bool disposing )
+        {
+            base.Dispose( disposing );
+            if (disposing == true)
+            {
+                if (this.credentialData != null)
+                {
+                    this.credentialData.Dispose();
+                }
+            }
+        }
+#endregion
+
+        /// <summary>
+        /// called on background thread by the framework to execute the action
+        /// </summary>
+        /// <param name="node"></param>
+        public override void OnRunNow(object sender)
+        {
+            if (this.configAction == ConfigAction.Drop)
+            {
+                if (this.credentialData.Credential != null)
+                {
+                    this.credentialData.Credential.DropIfExists();
+                }
+            }
+            else
+            {
+                this.credentialData.SendDataToServer();
+            }
+        }
+    }
+}