aws_rds_global_cluster: Add endpoint attribute for DB writer endpoint

.changelog/39960.txt

@@ -0,0 +1,3 @@
+```release-note:enhancement
+resource/aws_rds_global_cluster: Add `endpoint` argument to point to the writer DB instance in the current primary cluster
+```

internal/service/rds/global_cluster.go

@@ -61,6 +61,10 @@ func resourceGlobalCluster() *schema.Resource {
 				Optional: true,
 				Default:  false,
 			},
+			names.AttrEndpoint: {
+				Type:     schema.TypeString,
+				Computed: true,
+			},
 			names.AttrEngine: {
 				Type:          schema.TypeString,
 				Optional:      true,
@@ -210,6 +214,7 @@ func resourceGlobalClusterRead(ctx context.Context, d *schema.ResourceData, meta
 	d.Set(names.AttrARN, globalCluster.GlobalClusterArn)
 	d.Set(names.AttrDatabaseName, globalCluster.DatabaseName)
 	d.Set(names.AttrDeletionProtection, globalCluster.DeletionProtection)
+	d.Set(names.AttrEndpoint, globalCluster.Endpoint)
 	d.Set(names.AttrEngine, globalCluster.Engine)
 	d.Set("engine_lifecycle_support", globalCluster.EngineLifecycleSupport)
 	d.Set("global_cluster_identifier", globalCluster.GlobalClusterIdentifier)

internal/service/rds/global_cluster_test.go

@@ -124,6 +124,7 @@ func TestAccRDSGlobalCluster_basic(t *testing.T) {
 					resource.TestCheckResourceAttr(resourceName, "global_cluster_identifier", rName),
 					resource.TestMatchResourceAttr(resourceName, "global_cluster_resource_id", regexache.MustCompile(`cluster-.+`)),
 					resource.TestCheckResourceAttr(resourceName, names.AttrStorageEncrypted, acctest.CtFalse),
+					resource.TestCheckResourceAttrSet(resourceName, names.AttrEndpoint),
 				),
 			},
 			{

website/docs/r/rds_global_cluster.html.markdown

@@ -217,6 +217,7 @@ This resource supports the following arguments:
 This resource exports the following attributes in addition to the arguments above:
 
 * `arn` - RDS Global Cluster Amazon Resource Name (ARN)
+* `endpoint` - Writer endpoint for the new global database cluster. This endpoint always points to the writer DB instance in the current primary cluster.
 * `global_cluster_members` - Set of objects containing Global Cluster members.
     * `db_cluster_arn` - Amazon Resource Name (ARN) of member DB Cluster
     * `is_writer` - Whether the member is the primary DB Cluster