fix: set external_address for lb to optional

Author: Marcel Jacek

docs/resources/loadbalancer.md

@@ -119,7 +119,6 @@ resource "stackit_loadbalancer" "example" {
 
 ### Required
 
-- `external_address` (String) External Load Balancer IP address where this Load Balancer is exposed.
 - `listeners` (Attributes List) List of all listeners which will accept traffic. Limited to 20. (see [below for nested schema](#nestedatt--listeners))
 - `name` (String) Load balancer name.
 - `networks` (Attributes List) List of networks that listeners and targets reside in. (see [below for nested schema](#nestedatt--networks))
@@ -128,6 +127,7 @@ resource "stackit_loadbalancer" "example" {
 
 ### Optional
 
+- `external_address` (String) External Load Balancer IP address where this Load Balancer is exposed.
 - `options` (Attributes) Defines any optional functionality you want to have enabled on your load balancer. (see [below for nested schema](#nestedatt--options))
 - `region` (String) The resource region. If not defined, the provider region is used.
 

stackit/internal/services/loadbalancer/loadbalancer/resource.go

@@ -7,6 +7,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/hashicorp/terraform-plugin-framework-validators/resourcevalidator"
 	loadbalancerUtils "github.com/stackitcloud/terraform-provider-stackit/stackit/internal/services/loadbalancer/utils"
 
 	"github.com/google/uuid"
@@ -237,6 +238,16 @@ func (r *loadBalancerResource) ModifyPlan(ctx context.Context, req resource.Modi
 	}
 }
 
+// ConfigValidators validates the resource configuration
+func (r *loadBalancerResource) ConfigValidators(_ context.Context) []resource.ConfigValidator {
+	return []resource.ConfigValidator{
+		resourcevalidator.AtLeastOneOf(
+			path.MatchRoot("external_address"),
+			path.MatchRoot("options").AtName("private_network_only"),
+		),
+	}
+}
+
 // Configure adds the provider configured client to the resource.
 func (r *loadBalancerResource) Configure(ctx context.Context, req resource.ConfigureRequest, resp *resource.ConfigureResponse) {
 	var ok bool
@@ -327,7 +338,7 @@ The example below creates the supporting infrastructure using the STACKIT Terraf
 			},
 			"external_address": schema.StringAttribute{
 				Description: descriptions["external_address"],
-				Required:    true,
+				Optional:    true,
 				PlanModifiers: []planmodifier.String{
 					stringplanmodifier.RequiresReplace(),
 				},