Log Message:
databases/ruby-sequel: update to 5.42.0

5.42.0 (2021-03-01)

* Make the ado timestamp conversion proc a normal conversion proc that can
  be overridden similar to other conversion procs (jeremyevans)

* Add :reject_nil option to the nested_attributes method, to ignore calls
  where nil is passed as the associated object data (jeremyevans)

* Add async_thread_pool plugin for easier async usage with model classes and
  support for async destroy, with_pk, and with_pk! methods (jeremyevans)

* Add async_thread_pool Database extension for executing queries
  asynchronously using a thread pool (jeremyevans)

* Fix possible thread safety issue in Database#extension that could allow
  Module#extended to be called twice with the same Database instance
  (jeremyevans)

* Support cases where validations make modifications beyond setting errors
  in Model#freeze (jeremyevans)

* Add Model#to_json_data to the json_serializer plugin, returning a JSON
  data structure (jeremyevans)