containers: allow Ubuntu2404 for AKS os_sku

Changes:
- allow `Ubuntu2404` in the AKS node pool `os_sku` schema validation list
- allow `Ubuntu2404` in the AKS default node pool `os_sku` schema validation list
- add offline schema tests that lock in `Ubuntu2404` acceptance for both code paths

Validation:
- go test ./internal/services/containers -run "TestKubernetes.*Ubuntu2404" -count=1

Author: steveej

internal/services/containers/kubernetes_cluster_node_pool_resource.go

@@ -333,6 +333,7 @@ func resourceKubernetesClusterNodePoolSchema() map[string]*pluginsdk.Schema {
 				string(agentpools.OSSKUAzureLinuxThree),
 				string(agentpools.OSSKUUbuntu),
 				string(agentpools.OSSKUUbuntuTwoTwoZeroFour),
+				string(agentpools.OSSKUUbuntuTwoFourZeroFour),
 				string(agentpools.OSSKUWindowsTwoZeroOneNine),
 				string(agentpools.OSSKUWindowsTwoZeroTwoTwo),
 			}, false),

internal/services/containers/kubernetes_nodepool.go

@@ -191,6 +191,7 @@ func SchemaDefaultNodePool() *pluginsdk.Schema {
 							string(agentpools.OSSKUAzureLinuxThree),
 							string(agentpools.OSSKUUbuntu),
 							string(agentpools.OSSKUUbuntuTwoTwoZeroFour),
+							string(agentpools.OSSKUUbuntuTwoFourZeroFour),
 							string(agentpools.OSSKUWindowsTwoZeroOneNine),
 							string(agentpools.OSSKUWindowsTwoZeroTwoTwo),
 						}, false),

internal/services/containers/kubernetes_os_sku_validation_test.go

@@ -0,0 +1,42 @@
+// Copyright IBM Corp. 2014, 2025
+// SPDX-License-Identifier: MPL-2.0
+
+package containers
+
+import (
+	"testing"
+
+	"github.com/hashicorp/terraform-provider-azurerm/internal/tf/pluginsdk"
+)
+
+func TestKubernetesClusterNodePoolSchemaAcceptsUbuntu2404(t *testing.T) {
+	validate := resourceKubernetesClusterNodePoolSchema()["os_sku"].ValidateFunc
+	if validate == nil {
+		t.Fatal("node pool os_sku ValidateFunc is nil")
+	}
+
+	if warnings, errs := validate("Ubuntu2404", "os_sku"); len(warnings) != 0 || len(errs) != 0 {
+		t.Fatalf("expected Ubuntu2404 to be accepted for node pool os_sku, got warnings=%v errs=%v", warnings, errs)
+	}
+}
+
+func TestKubernetesClusterDefaultNodePoolSchemaAcceptsUbuntu2404(t *testing.T) {
+	defaultNodePool := resourceKubernetesCluster().Schema["default_node_pool"]
+	if defaultNodePool == nil {
+		t.Fatal("default_node_pool schema is nil")
+	}
+
+	defaultNodePoolResource, ok := defaultNodePool.Elem.(*pluginsdk.Resource)
+	if !ok {
+		t.Fatalf("expected default_node_pool elem to be a resource, got %T", defaultNodePool.Elem)
+	}
+
+	validate := defaultNodePoolResource.Schema["os_sku"].ValidateFunc
+	if validate == nil {
+		t.Fatal("default node pool os_sku ValidateFunc is nil")
+	}
+
+	if warnings, errs := validate("Ubuntu2404", "os_sku"); len(warnings) != 0 || len(errs) != 0 {
+		t.Fatalf("expected Ubuntu2404 to be accepted for default node pool os_sku, got warnings=%v errs=%v", warnings, errs)
+	}
+}