This reverts commit 536d3068.

Flush idle database connections

minor Engines guide copyedits: neutral language,  verb tense, comma splice [ci skip]

When load `5.1` config, `form_with_generates_remote_forms` is set.
https://github.com/rails/rails/blob/89a209f1abba5a2320d31c4898dea150c0abd0c0/railties/lib/rails/application/configuration.rb#L86

Provide arguments to RecordNotFound

Fix names of http authentication modules in api only guides

form_with_generates_ids

Own style guide says we should be using parentheses for method calls
with arguments.

Allow skip_default_ids option to be set in form_with

Improved logging of AJ's DelayedJob wrapper

When the defaults being loaded are the 5.0 or 5.1 we disable generation
of ids with form_with.

When `form_with` was introduced we disabled the automatic
generation of ids that was enabled in `form_for`. This usually
is not an good idea since labels don't work when the input
doesn't have an id and it made harder to test with Capybara.

You can still disable the automatic generation of ids setting
`config.action_view.form_with_generates_ids` to `false.`

Even that collisions are unlikely we need to make sure the two strings
are equal.

Timing is not important in this case because this only runs after the
comparison between the SHA256 digested strings returns true.

Make variable_size_secure_compare public

Add :nodoc: to activerecord [ci skip]

Ordinal methods should respect loaded records

Update guide layout [ci skip]

* [ci skip] SecureRandom should mentioned Win32 CryptoAPI functions instead of Win32

* Remove functions word

Improve AR connection fork safety

Rubocop style: Missing magic comment

Update documentation to lead with ajax param `event.detail` [ci skip]

[ci skip] Rails Associations examples contains ActiveRecord::Base ref…

Fix tld_length documentation in ActionDispatch::Cookies [ci skip]

[ci skip] Rails Associations examples contains ActiveRecord::Base reference instead of ApplicationRecord in images

ActiveJob wraps every adapter into its own class, that is later passed
into DelayedJob which is responsible for displaying all the logs.

This change improves the logging so we can easily trace executed
jobs and see meaningful information in the logs.

Correct render method's response header's content type for option(:body) from text/html to text/plain. (#31212)

Fix unstable test test_delegate_socket_errors_to_on_error_handler

I often face the following error when running test/connection/client_socket_test.rb:

```
$ bin/test test/connection/client_socket_test.rb:38
Run options: --seed 44035

# Running:

F

Failure:
ActionCable::Connection::ClientSocketTest#test_delegate_socket_errors_to_on_error_handler
[/app/actioncable/test/connection/client_socket_test.rb:47]:
--- expected
+++ actual
@@ -1 +1 @@
-["foo"]
+["Broken pipe", "Broken pipe", "Broken pipe", "foo"]
```

It can be reproduced easily by applying the following patch:

```
diff --git a/actioncable/test/connection/client_socket_test.rb b/actioncable/test/connection/client_socket_test.rb
index 2051216010..6bb9f13ea7 100644
--- a/actioncable/test/connection/client_socket_test.rb
+++ b/actioncable/test/connection/client_socket_test.rb
@@ -34,7 +34,8 @@ def on_error(message)
     @server.config.allowed_request_origins = %w( http://rubyonrails.com )
   end

-  test "delegate socket errors to on_error handler" do
+  1000.times do |i|
+  test "delegate socket errors to on_error handler #{i}" do
     run_in_eventmachine do
       connection = open_connection

@@ -47,6 +48,7 @@ def on_error(message)
       assert_equal %w[ foo ], connection.errors
     end
   end
+  end

   test "closes hijacked i/o socket at shutdown" do
     run_in_eventmachine do
```

The cause is writing io from different thread at the same time.

`connection.process` sends handshake message from [StreamEventLoop's thread][] whereas
`connection.handle_open` sends welcome message from current thread.

[StreamEventLoop's thread]: https://github.com/rails/rails/blob/067fc779c4560fff4812614a2f78f9248f3e55f8/actioncable/lib/action_cable/connection/stream_event_loop.rb#L75