SQL Agent configuration for Operators, Alerts and Proxies (WIP) (#621)

* Initial non-refactored SQL Agent alert classes (WIP)

* Move agent classes into subdirectories

* Refactor the agent config code a bit more

* Add more implementation for handlers

* Add more code to the create alert handler

* Clean up agent alert class

* Clean up alert methods a bit

* Initial Operator contracts

* Additonal SQL Agent config changes

* More Proxy config cleanup

* Cleanup AgentProxy class

* Additional cleanups

* Run SRGen

* Add security service to create credential objects

src/Microsoft.SqlTools.ServiceLayer/Security/Contracts/CredentialRequest.cs

@@ -0,0 +1,45 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+using Microsoft.SqlTools.Hosting.Protocol.Contracts;
+using Microsoft.SqlTools.ServiceLayer.Utility;
+using Microsoft.SqlTools.Utility;
+
+namespace Microsoft.SqlTools.ServiceLayer.Security.Contracts
+{
+    /// <summary>
+    /// Create Credential parameters
+    /// </summary>
+    public class CreateCredentialParams : GeneralRequestDetails
+    {
+        public string OwnerUri { get; set; }
+
+        public CredentialInfo Credential { get; set; }
+    }
+
+    /// <summary>
+    /// Create Credential result
+    /// </summary>
+    public class CreateCredentialResult
+    {
+
+        public bool Succeeded { get; set; }
+
+        public string ErrorMessage { get; set; }
+    }
+
+    /// <summary>
+    /// Create Credential request type
+    /// </summary>
+    public class CreateCredentialRequest
+    {
+        /// <summary>
+        /// Request definition
+        /// </summary>
+        public static readonly
+            RequestType<CreateCredentialParams, CreateCredentialResult> Type =
+            RequestType<CreateCredentialParams, CreateCredentialResult>.Create("security/createcredential");
+    }
+}