chore: Updates mongodbatlas_advanced_cluster tests to expect temporary SERVICE_UNAVAILABLE error when migrating from old to new schema (#2523)

Author: maastha

internal/service/advancedcluster/resource_advanced_cluster_migration_test.go

@@ -3,6 +3,7 @@ package advancedcluster_test
 import (
 	"fmt"
 	"os"
+	"regexp"
 	"testing"
 
 	"github.com/hashicorp/terraform-plugin-testing/helper/resource"
@@ -104,6 +105,11 @@ func TestMigAdvancedCluster_shardedMigrationFromOldToNewSchema(t *testing.T) {
 				Config:            configShardedTransitionOldToNewSchema(orgID, projectName, clusterName, false),
 				Check:             checkShardedTransitionOldToNewSchema(false),
 			},
+			{
+				ProtoV6ProviderFactories: acc.TestAccProviderV6Factories,
+				Config:                   configShardedTransitionOldToNewSchema(orgID, projectName, clusterName, true),
+				ExpectError:              regexp.MustCompile("SERVICE_UNAVAILABLE"),
+			},
 			{
 				ProtoV6ProviderFactories: acc.TestAccProviderV6Factories,
 				Config:                   configShardedTransitionOldToNewSchema(orgID, projectName, clusterName, true),
@@ -129,6 +135,11 @@ func TestMigAdvancedCluster_geoShardedMigrationFromOldToNewSchema(t *testing.T)
 				Config:            configGeoShardedTransitionOldToNewSchema(orgID, projectName, clusterName, false),
 				Check:             checkGeoShardedTransitionOldToNewSchema(false),
 			},
+			{
+				ProtoV6ProviderFactories: acc.TestAccProviderV6Factories,
+				Config:                   configShardedTransitionOldToNewSchema(orgID, projectName, clusterName, true),
+				ExpectError:              regexp.MustCompile("SERVICE_UNAVAILABLE"),
+			},
 			{
 				ProtoV6ProviderFactories: acc.TestAccProviderV6Factories,
 				Config:                   configGeoShardedTransitionOldToNewSchema(orgID, projectName, clusterName, true),