Acceptance Criteria

• Remove callbacks from all public method signatures (in the next major version) and delete the associated tests
  • Update corresponding function declarations to `async`
• Remove support for snappy v6

Testing Requirements

• Update any remaining tests that rely on callbacks to use promises instead

Documentation Requirements

• Remove callbacks from all examples that will be reused for V5 driver
  • Refer users to legacy client
• Add snappy and callback removal notes to breaking changes list
  • Defer detailed legacy client examples to separate ticket NODE-4523