Sku_name or Sku for azurerm_sql_database not expected

So I am trying to add a Azure SQL DB and I want to set the compute + storage as standard dtu based but when I’ve put either sku_name=“S1” or sku {} within the resource, CLI is saying “An argument named “sku_name” is not expected here.”

e.g.

# Database
resource "azurerm_sql_database" "sql_database" {
  name                = "test-db"
  resource_group_name = azurerm_resource_group.resource_group.name
  location            = azurerm_resource_group.resource_group.location
  server_name         = azurerm_sql_server.sql_server.name
  collation = "SQL_Latin1_General_CP1_CI_AS"
  max_size_gb    = 50
  sku_name  = "S1"
  extended_auditing_policy {
    storage_endpoint                        = azurerm_storage_account.storage_account.primary_blob_endpoint
    storage_account_access_key              = azurerm_storage_account.storage_account.primary_access_key
    storage_account_access_key_is_secondary = true
    retention_in_days                       = 7
  }
  tags = {
    environment = "TEST"
  }
}

I would like to set the DB as Standard DTU of 20 with 100GB. If I don’t have a place to put this sku, it will set the default as GP_Gen5_2. TIA.