Set AuthContext to null during disconnect.

Author: peombwa

src/Authentication/Authentication.Test/Helpers/GraphSessionTests.cs

@@ -15,7 +15,7 @@ public void GraphSessionShouldBeInitilizedAfterInitializerIsCalled()
         }
 
         [Fact]
-        public void ShoudlOverwriteExistingGraphSession()
+        public void ShouldOverwriteExistingGraphSession()
         {
             GraphSessionInitializer.InitializeSession();
             Guid originalSessionId = GraphSession.Instance._graphSessionId;
@@ -27,7 +27,7 @@ public void ShoudlOverwriteExistingGraphSession()
         } 
 
         [Fact]
-        public void ShoudlNotOverwriteExistingGraphSession()
+        public void ShouldNotOverwriteExistingGraphSession()
         {
             GraphSessionInitializer.InitializeSession();
             Guid originalSessionId = GraphSession.Instance._graphSessionId;

src/Authentication/Authentication/Cmdlets/DisconnectGraph.cs

@@ -31,7 +31,7 @@ protected override void ProcessRecord()
 
             AuthenticationHelpers.Logout(authConfig);
 
-            SessionState.PSVariable.Remove(Constants.GraphAuthConfigId);
+            GraphSession.Instance.AuthContext = null;
         }
 
         protected override void StopProcessing()

src/Authentication/Authentication/Common/GraphSession.cs

@@ -7,9 +7,9 @@ namespace Microsoft.Graph.PowerShell.Authentication
     using System;
     using System.Threading;
     /// <summary>
-    /// The current <see cref="GraphSession"/>.
+    /// Contains methods to create, modify or obtain a thread safe static instance of <see cref="GraphSession"/>.
     /// </summary>
-    public class GraphSession: IGraphSession
+    public class GraphSession : IGraphSession
     {
         static GraphSession _instance;
         static bool _initialized = false;
@@ -50,6 +50,9 @@ public static GraphSession Instance
                 }
             }
         }
+        /// <summary>
+        /// Creates a new GraphSession.
+        /// </summary>
         public GraphSession()
         {
             _graphSessionId = Guid.NewGuid();

src/Authentication/Authentication/Models/AuthContext.cs

@@ -3,10 +3,8 @@
 // ------------------------------------------------------------------------------
 namespace Microsoft.Graph.PowerShell.Authentication
 {
-    using Newtonsoft.Json;
     public class AuthContext: IAuthContext
     {
-        [JsonIgnore]
         private const string PowerShellClientId = "14d82eec-204b-4c2f-b7e8-296a70dab67e";
         public string ClientId { get; set; }
         public string TenantId { get; set; }