Fix identity block and NAT gateway prefix length documentation

Agent-Logs-Url: https://github.com/localstack/localstack-azure-samples/sessions/e100db37-5dea-4c4e-a4aa-4aad5ef381bd

Co-authored-by: paolosalvatori <1658419+paolosalvatori@users.noreply.github.com>

Author: Copilot

samples/web-app-custom-image/python/terraform/modules/nat_gateway/variables.tf

@@ -49,7 +49,7 @@ variable "public_ip_prefix_name" {
 }
 
 variable "public_ip_prefix_length" {
-  description = "(Required) The length of the public IP prefix to create and associate with the NAT Gateway. Must be between 28 and 30."
+  description = "(Required) The length of the public IP prefix to create and associate with the NAT Gateway. Must be between 28 and 31."
   type        = number
   default     = 31
 }

samples/web-app-custom-image/python/terraform/modules/web_app/main.tf

@@ -9,9 +9,12 @@ resource "azurerm_linux_web_app" "example" {
   client_affinity_enabled       = false
   tags                          = var.tags
 
-  identity {
-    type         = "UserAssigned"
-    identity_ids = var.managed_identity_id != null ? [var.managed_identity_id] : []
+  dynamic "identity" {
+    for_each = var.managed_identity_id != null ? [1] : []
+    content {
+      type         = "UserAssigned"
+      identity_ids = [var.managed_identity_id]
+    }
   }
 
   site_config {