Set SKE extension Argus instance ID field to Optional (#502)

Author: joaopalet

docs/resources/ske_cluster.md

@@ -131,9 +131,12 @@ Required:
 
 Required:
 
-- `argus_instance_id` (String) Argus instance ID to choose which Argus instance is used. Required when enabled is set to `true`.
 - `enabled` (Boolean) Flag to enable/disable Argus extensions.
 
+Optional:
+
+- `argus_instance_id` (String) Argus instance ID to choose which Argus instance is used. Required when enabled is set to `true`.
+
 
 <a id="nestedatt--extensions--dns"></a>
 ### Nested Schema for `extensions.dns`

stackit/internal/services/ske/cluster/resource.go

@@ -582,7 +582,7 @@ func (r *clusterResource) Schema(_ context.Context, _ resource.SchemaRequest, re
 							},
 							"argus_instance_id": schema.StringAttribute{
 								Description: "Argus instance ID to choose which Argus instance is used. Required when enabled is set to `true`.",
-								Required:    true,
+								Optional:    true,
 							},
 						},
 					},