Fix grafana_cloud_service_account read

Regression from #1412
In that PR, I noticed that the ID format for the stack service account is incomplete
It contained only the SA ID, and without the stack slug, it didn't really allow for imports
I fixed it, but now read operations from the old ID format didn't work anymore

To fix this, we can support the old ID format (just the SA ID) until the next major version

This is unfortunately not testable with the acceptance test framework, but I tested it manually

internal/resources/cloud/resource_cloud_stack_service_account.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 	"net/url"
+	"strconv"
 	"time"
 
 	"github.com/grafana/grafana-com-public-clients/go/gcom"
@@ -100,18 +101,31 @@ func createStackServiceAccount(ctx context.Context, d *schema.ResourceData, clou
 }
 
 func readStackServiceAccount(ctx context.Context, d *schema.ResourceData, cloudClient *gcom.APIClient) diag.Diagnostics {
-	split, err := resourceStackServiceAccountID.Split(d.Id())
-	if err != nil {
-		return diag.FromErr(err)
+	var stackSlug string
+	var serviceAccountID int64
+	split, splitErr := resourceStackServiceAccountID.Split(d.Id())
+	if splitErr != nil {
+		// ID used to be just the service account ID.
+		// Even though that's an incomplete ID for imports, we need to handle it for backwards compatibility
+		// TODO: Remove on next major version
+		stackSlug = d.Get("stack_slug").(string)
+		var parseErr error
+		if serviceAccountID, parseErr = strconv.ParseInt(d.Id(), 10, 64); parseErr != nil {
+			return diag.Errorf("failed to parse ID (%s) as stackSlug:serviceAccountID: %v and failed to parse as serviceAccountID: %v", d.Id(), splitErr, parseErr)
+		}
+	} else {
+		stackSlug, serviceAccountID = split[0].(string), split[1].(int64)
 	}
-	stackSlug, serviceAccountID := split[0].(string), split[1].(int64)
 
 	client, cleanup, err := CreateTemporaryStackGrafanaClient(ctx, cloudClient, stackSlug, "terraform-temp-")
 	if err != nil {
 		return diag.FromErr(err)
 	}
 	defer cleanup()
 
+	d.Set("stack_slug", stackSlug)
+	d.SetId(resourceStackServiceAccountID.Make(stackSlug, serviceAccountID))
+
 	return readStackServiceAccountWithClient(client, d, serviceAccountID)
 }
 
@@ -162,6 +176,8 @@ func updateStackServiceAccount(ctx context.Context, d *schema.ResourceData, clou
 	if _, err := client.ServiceAccounts.UpdateServiceAccount(updateRequest); err != nil {
 		return diag.FromErr(err)
 	}
+	d.Set("stack_slug", stackSlug)
+	d.SetId(resourceStackServiceAccountID.Make(stackSlug, serviceAccountID))
 
 	return readStackServiceAccountWithClient(client, d, serviceAccountID)
 }

internal/resources/cloud/resource_cloud_stack_service_account_test.go

@@ -47,6 +47,11 @@ func TestAccGrafanaServiceAccountFromCloud(t *testing.T) {
 					resource.TestCheckResourceAttr("grafana_cloud_stack_service_account.management", "is_disabled", "false"),
 				),
 			},
+			{
+				ImportState:       true,
+				ResourceName:      "grafana_cloud_stack_service_account.management",
+				ImportStateVerify: true,
+			},
 			{
 				Config: testAccStackConfigBasic(slug, slug, "description"),
 				Check:  testAccGrafanaAuthCheckServiceAccounts(&stack, []string{}),