fix ExecStatus (#881)

* fix ExecStatus

* add missing file

src/KubernetesClient.Models/KubeConfigModels/ExecCredentialResponse.cs

@@ -5,7 +5,7 @@ namespace k8s.KubeConfigModels
         public class ExecStatus
         {
 #nullable enable
-            public DateTime? Expiry { get; set; }
+            public DateTime? ExpirationTimestamp { get; set; }
             public string? Token { get; set; }
             public string? ClientCertificateData { get; set; }
             public string? ClientKeyData { get; set; }

src/KubernetesClient/Authentication/ExecTokenProvider.cs

@@ -23,12 +23,12 @@ namespace k8s.Authentication
                 return true;
             }
 
-            if (response.Status.Expiry == null)
+            if (response.Status.ExpirationTimestamp == null)
             {
                 return false;
             }
 
-            return DateTime.UtcNow.AddSeconds(30) > response.Status.Expiry;
+            return DateTime.UtcNow.AddSeconds(30) > response.Status.ExpirationTimestamp;
         }
 
         public async Task<AuthenticationHeaderValue> GetAuthenticationHeaderAsync(CancellationToken cancellationToken)