Azure – Terraform azapi_resource for Microsoft.Web/certificates@2021-02-01 no longer working

I am using Terraform 1.8.0.

I am trying to create a Azure Managed cert. based on a cert. held in a Azure Key-Vault (stored as a secret).

Terraform locals file…

az_managed_ssl_cert_name = "ssl-wildcard-ds-UK-ABC-certabcdefghijkl"

Terraform main.tf…

    # ASP for Re-Id Function-Apps
module "app_service_plan_03" {
  source               = "../../resource_modules/app_service_plan"
  os_type              = var.os_type_fapps_re_id
  sku_name             = var.sku_name_fapps_re_id
  location             = var.location
  rg                   = local.re_id_rg_name
  name                 = local.app_service_plan_03
  max_worker_count     = var.max_app_service_plan_01_worker_count_re_id
  min_worker_count     = var.min_app_service_plan_01_worker_count_re_id
  law_id               = data.azurerm_log_analytics_workspace.law.id
  enable_resource_lock = var.re_id_enable_asp_resource_lock
}



resource "azapi_resource" "cert" {
          depends_on = [data.azurerm_subscription.current]
          type       = "Microsoft.Web/certificates@2021-02-01"
          name       = var.cert_name
          parent_id  = local.certificate_resource_group # Resource Group name where certificate is created.
    
      body = jsonencode({
        "location" : var.location,
        "properties" : {
          "serverFarmId" : data.azurerm_service_plan.asp.id,
          "keyVaultId" : data.azurerm_key_vault.kv_certs.id, # The Azure Key vault that stores the SSL certificates is in the 'Production' subscription.
          "keyVaultSecretName" : local.az_managed_ssl_cert_name
        }
      })
    }

When I build the Terraform it reports an error. I then stripped the code back to just…

    resource "azapi_resource" "cert" {
  depends_on = [data.azurerm_subscription.current, module.app_service_plan_03, data.azurerm_key_vault.kv_certs]
  type       = "Microsoft.Web/certificates@2021-02-01"
  name       = local.cert_name
  parent_id  = module.create_resource_group.id

  body = jsonencode({
    "location" : var.location,
    "properties" : {
      "keyVaultSecretName" : "abcdef"
    }
  })
}

The error reported is with the body…

    │ Error: Invalid body
    │ 
    │   with azapi_resource.cert,
    │   on main.tf line 206, in resource "azapi_resource" "cert":
    │  206: resource "azapi_resource" "cert" {
    │ 
    │ The argument "body" is invalid: unmarshaling failed: value:
    │ "{"location":"uksouth","properties":{"keyVaultSecretName":"abcdef"}}",
    │ err: json: cannot unmarshal string into Go value of type
    │ map[string]interface {}
    ╵
    ╷
    │ Error: Invalid Type
    │ 
    │   with azapi_resource.cert,
    │   on main.tf line 212, in resource "azapi_resource" "cert":
    │  212:   body = jsonencode({
    │  213:     "location" : var.location,
    │  214:     "properties" : {
    │  215:       "keyVaultSecretName" : "abcdef"
    │  216:     }
    │  217:   })

│ 
│ The value must not be a string

I don’t understand where I am going wrong – any advice would be appreciated?