* Introduce a connection coder responsible for encoding Cable messages
  as WebSocket messages, defaulting to `ActiveSupport::JSON` and duck-
  typing to any object responding to `#encode` and `#decode`.
* Consolidate encoding responsibility to the connection. No longer
  explicitly JSON-encode from channels or other sources. Pass Cable
  messages as Hashes to `#transmit` and rely on it to encode.
* Introduce stream encoders responsible for decoding pubsub messages.
  Preserve the currently raw encoding, but make it easy to use JSON.
  Same duck type as the connection encoder.
* Revert recent data normalization/quoting (#23649) which treated
  `identifier` and `data` values as nested JSON objects rather than as
  opaque JSON-encoded strings. That dealt us an awkward hand where we'd
  decode JSON strings… or not, but always encode as JSON. Embedding
  JSON object values directly is preferably, no extra JSON encoding,
  but that should be a purposeful protocol version change rather than
  ambiguously, inadvertently supporting multiple message formats.

Cable: reconcile default worker pool size with low db conn pool size

Whack it down from 100 to 4.

Large worker pools means large db connection counts. We aren't set up
for that by default and most apps won't need it out of the box.

We're better off tuning the default worker pool for low traffic, low
resource consumption apps. Those who have higher traffic will scale up
to meet demand.

Make to private the visibility of `_quote` and `_type_cast`

Replace _meth with _method to remove ambiguity

[ci skip]

Update Gemfile.lock

Suppress warnings

'rake' gem is bundled to '>= 11.1' by 30279704
(#23499), but it seems the commit did not fully include Gemfile.lock's.

"Using a dynamic :controller (or :action) segment in a route is deprecated"
by 6520ea5f (#23980).

provide file name for fixture ERB

Run one JRuby worker on CI; allow to fail

Uses latest precompiled JRuby so that
we don't spend time downloading versions Travis has
not already compiled. http://rubies.travis-ci.org/

Uses latest jdk: oraclejdk8
per
https://docs.travis-ci.com/user/build-environment-updates/2015-02-03/#Ruby-VM
and
https://docs.travis-ci.com/user/languages/ruby/#Supported-Ruby-Versions-and-RVM

Follows on work in https://github.com/rails/rails/pull/23927 which was reverted
https://github.com/rails/rails/commit/26fe5fa08d52384bcea09c4210e3b3baaf5e9b95

JRUBY_OPTS minimize GC, disable JIT, for max test speed
  - https://github.com/rails/rails/pull/16613
  - https://github.com/rails/rails/pull/17088

Have Rails use JRuby-compatible Rake 11.1
  - The Rake task was passing --verbose, an invalid option, to contemporary JRuby
  - https://github.com/ruby/rake/pull/120
  - https://github.com/rails-api/active_model_serializers/pull/1585
  - https://github.com/jruby/jruby/issues/3653#issuecomment-195883717

No advantage to directly mounting JRuby over installing from cache; both on S3
  - https://github.com/rails/rails/pull/23499/commits/b2d5b336b5a812009444571b22eed90777cd9a8c
  - https://github.com/rails/rails/pull/23499/commits/f4fad041b2755d81e82ee3fc66d96f334b4653db

Pass over CHANGELOGs [ci skip]

Fix rails restart issue with Puma

- We need to pass the restart command to Puma so that it will use it
  while restarting the server.
- Also made sure that all the options passed by user while starting
  the server are used in the generated restart command so that they will
  be used while restarting the server.
- Besides that we need to remove the server.pid file for the previous running
  server because otherwise Rack complains about it's presence.
- We don't care if the server.pid file does not exist. We only want to delete
  it if it exists.
- This also requires some changes on Puma side which are being tracked
  here - https://github.com/puma/puma/pull/936.
- Fixes #23910.

Fix deprecation warning for ParamsParser instance 😄

Related with 38d2bf5f.

cc @tenderlove

Add upcase_first method

To move Action Cable logging to a LoggingSubscriber we need to pass the
log tags in the notification payload since Action Cable logging use the
Channel instance to tag the logs.

Add a test case for create a record with primary key as zero

Remove `except` helper for test schema

Add ActiveSupport::Notification to Channel::Base#perform_action

Add changelog for #24305

Update compatibility.rb

update `assert_no_performed_jobs` doc to use `assert_no_performed_jobs` method [ci skip]

Delegate some additional methods in querying.rb

Fix typo in headers comment [ci skip]

Forgot to add, sigh.

Closes #24273