v8.8.0b1

• #1270 Update generated code for beta
  • Add support for new resources Billing.MeterEventAdjustment, Billing.MeterEvent, and Billing.Meter
  • Add support for create, deactivate, list, modify, reactivate, and retrieve methods on resource Meter
  • Add support for create method on resources MeterEventAdjustment and MeterEvent
  • Add support for create test helper method on resource ConfirmationToken
  • Add support for add_lines, remove_lines, and update_lines methods on resource Invoice
• #1266 Beta: record usage of async interface

See the changelog for more details.