chore: Remove doc notes of SERVICE_UNAVAILABLE error and redundant logic in check exists (#3286)

* remove doc notes of SERVICE_UNAVAILABLE error and redundant logic in check exists

* lint error

* remove unnecessary function definition

Author: AgustinBettati

docs/guides/advanced-cluster-new-sharding-schema.md

@@ -87,8 +87,6 @@ resource "mongodbatlas_advanced_cluster" "test" {
 
 This updated configuration will trigger a Terraform update plan. However, the underlying cluster will not face any changes after the `apply` command, as both configurations represent a sharded cluster composed of two shards.
 
-Note: The first time `terraform apply` command is run **after** updating the configuration, you may receive a `500 Internal Server Error (Error code: "SERVICE_UNAVAILABLE")` error. This is a known temporary issue. If you encounter this, please re-run `terraform apply` and this time the update should succeed. 
-
 <a id="migration-geosharded"></a>
 ### Migrate advanced_cluster type `GEOSHARDED`
 
@@ -197,8 +195,6 @@ resource "mongodbatlas_advanced_cluster" "test" {
 
 This updated configuration triggers a Terraform update plan. However, the underlying cluster will not face any changes after the `apply` command, as both configurations represent a geo sharded cluster with two zones and two shards in each one.
 
-Note: The first time `terraform apply` command is run **after** updating the configuration, you may receive a `500 Internal Server Error (Error code: "SERVICE_UNAVAILABLE")` error. This is a known temporary issue. If you encounter this, please re-run `terraform apply` and this time the update should succeed. 
-
 <a id="migration-replicaset"></a>
 ### Migrate advanced_cluster type `REPLICASET`
 
@@ -285,8 +281,6 @@ resource "mongodbatlas_advanced_cluster" "test" {
 }
 ```
 
-Note: The first time `terraform apply` command is run **after** updating the configuration, you may receive a `500 Internal Server Error (Error code: "SERVICE_UNAVAILABLE")` error. This is a known temporary issue. If you encounter this, please re-run `terraform apply` and this time the update should succeed. 
-
 <a id="use-iss"></a>
 ## Use Independent Shard Scaling 
 

docs/resources/advanced_cluster (preview provider 2.0.0).md

@@ -935,7 +935,6 @@ See detailed information for arguments and attributes: [MongoDB API Advanced Clu
 
 ~> **IMPORTANT:**
 <br> &#8226; When a cluster is imported, the resulting schema structure will always return the new schema including `replication_specs` per independent shards of the cluster.
-<br> &#8226;  Note: The first time `terraform apply` command is run **after** updating the configuration of an imported cluster, you may receive a `500 Internal Server Error (Error code: "SERVICE_UNAVAILABLE")` error. This is a known temporary issue. If you encounter this, please re-run `terraform apply` and this time the update should succeed. 
 
 ## Move
 

docs/resources/advanced_cluster.md

@@ -767,7 +767,6 @@ See detailed information for arguments and attributes: [MongoDB API Advanced Clu
 
 ~> **IMPORTANT:**
 <br> &#8226; When a cluster is imported, the resulting schema structure will always return the new schema including `replication_specs` per independent shards of the cluster.
-<br> &#8226;  Note: The first time `terraform apply` command is run **after** updating the configuration of an imported cluster, you may receive a `500 Internal Server Error (Error code: "SERVICE_UNAVAILABLE")` error. This is a known temporary issue. If you encounter this, please re-run `terraform apply` and this time the update should succeed. 
 
 ## Considerations and Best Practices
 

internal/service/cloudbackupsnapshot/resource_cloud_backup_snapshot_test.go

@@ -112,8 +112,8 @@ func checkExists(resourceName string) resource.TestCheckFunc {
 		if _, _, err := acc.ConnV2().CloudBackupsApi.GetReplicaSetBackup(context.Background(), ids["project_id"], ids["cluster_name"], ids["snapshot_id"]).Execute(); err != nil {
 			return fmt.Errorf("cloudBackupSnapshot (%s) does not exist", rs.Primary.Attributes["snapshot_id"])
 		}
-		// needed as first call to cluster with new API will fail due to transition to ISS feature flag
-		if err := acc.CheckExistsClusterHandlingRetry(ids["project_id"], ids["cluster_name"]); err != nil {
+
+		if _, _, err := acc.ConnV2().ClustersApi.GetCluster(context.Background(), ids["project_id"], ids["cluster_name"]).Execute(); err != nil {
 			return fmt.Errorf("cluster (%s : %s) does not exist", ids["project_id"], ids["cluster_name"])
 		}
 		return nil

internal/testutil/acc/advanced_cluster.go

@@ -103,26 +103,13 @@ func CheckExistsCluster(resourceName string) resource.TestCheckFunc {
 		if projectID == "" || clusterName == "" {
 			return fmt.Errorf("projectID or clusterName is empty: %s, %s", projectID, clusterName)
 		}
-		if err := CheckExistsClusterHandlingRetry(projectID, clusterName); err != nil {
+		if _, _, err := ConnV2().ClustersApi.GetCluster(context.Background(), projectID, clusterName).Execute(); err != nil {
 			return fmt.Errorf("cluster(%s:%s) does not exist: %w", projectID, clusterName, err)
 		}
 		return nil
 	}
 }
 
-func CheckExistsClusterHandlingRetry(projectID, clusterName string) error {
-	return retry.RetryContext(context.Background(), 3*time.Minute, func() *retry.RetryError {
-		if _, _, err := ConnV2().ClustersApi.GetCluster(context.Background(), projectID, clusterName).Execute(); err != nil {
-			if admin.IsErrorCode(err, "SERVICE_UNAVAILABLE") {
-				// retrying get operation because for migration test it can be the first time new API is called for a cluster so API responds with temporary error as it transition to enabling ISS FF
-				return retry.RetryableError(err)
-			}
-			return retry.NonRetryableError(err)
-		}
-		return nil
-	})
-}
-
 func CheckFCVPinningConfig(usePreviewProvider bool, resourceName, dataSourceName, pluralDataSourceName string, mongoDBMajorVersion int, pinningExpirationDate *string, fcvVersion *int) resource.TestCheckFunc {
 	mapChecks := map[string]string{
 		"mongo_db_major_version": fmt.Sprintf("%d.0", mongoDBMajorVersion),