v20.4.0-alpha.4

• #2574 Update generated code for private-preview
  • ⚠️ Add support for new value spend_threshold on enums Billing.Alert.alert_type, Billing.AlertCreateParams.alert_type, and Billing.AlertListParams.alert_type
  • Add support for spend_threshold on Billing.AlertCreateParams and Billing.Alert
  • Add support for invoice_item, proration_details, proration, and subscription on InvoiceLineItem.parent.schedule_details
  • Add support for custom on PaymentMethodUpdateParams
  • Add support for payment_method_reference and usage on PaymentMethod.custom
  • Add support for outstanding_usage_through and unused_time_from on SubscriptionPauseParams.bill_for
  • ⚠️ Remove support for outstanding_usage and unused_time on SubscriptionPauseParams.bill_for
  • ⚠️ Remove support for payment_behavior on SubscriptionResumeParams

See the changelog for more details.