Follow up #37266.

`@pairs` is an array of arrays, not a hash.

`send` is not necessary.

The method add_template_helper is private and used only in one place.
I guess its purpose was to remove the noise of module_eval at the cost
of an indirection.

However, Module#include is public since Ruby 2.1, and the indirection
is no longer justified for my taste. The loop in the caller is more
straightforward now.

Add CacheStore connection pool docs to guide

When using Puma or another threaded server it is useful to know about
connection pool options for the cache stores. This commit explains how
to configure and enable the connection pool in the guides.

Update code return value in debugging rails guide [ci skip]

Now @_start_transaction_state set to nil instead of empty hash from https://github.com/rails/rails/commit/b1458218c95d85c4ce911dd3e99da5ae7cf7aeee.

Update Migration number to ensure consistency on the document [ci skip]

Updated Migration number to 6.0 as there were cases where it did show 5.0 and 5.2 which may lead to confusion on a newcomer reader.

Document the return value of update_all [ci skip]

Use the model's adapter for the attribute type lookup

Update Migration number from 5.0 to current 6.0 [ci skip]

Follow-up of 1ee4a881.

Move advisory lock to it's own connection

This PR moves advisory lock to it's own connection instead of
`ActiveRecord::Base` to fix #37748. As a note the issue is present on
both mysql and postgres. We don't see it on sqlite3 because sqlite3
doesn't support advisory locks.

The underlying problem only appears if:

1) the app is using multiple databases, and therefore establishing a new
connetion in the abstract models
2) the app has a migration that loads a model (ex `Post.update_all`)
which causes that new connection to get established.

This is because when Rails runs migrations the default connections are
established, the lock is taken out on the `ActiveRecord::Base`
connection. When the migration that calls a model is loaded, a new
connection will be established and the lock will automatically be
released.

When Rails goes to release the lock in the ensure block it will find
that the connection has been closed. Even if the connection wasn't
closed the lock would no longer exist on that connection.

We originally considered checking if the connection was active, but
ultimately that would hide that the advisory locks weren't working
correctly because there'd be no lock to release.

We also considered making the lock more granular - that it only blocked
on each migration individually instead of all the migrations for that
connection. This might be the right move going forward, but right now
multi-db migrations that load models are very broken in Rails 6.0 and
master.

John and I don't love this fix, it requires a bit too much knowledge of
internals and how Rails picks up connections. However, it does fix the
issue, makes the lock more global, and makes the lock more resilient to
changing connections.
Co-authored-by: NJohn Crepezzi <john.crepezzi@gmail.com>

Allow updating the database selector context with the response and not only the request

Use path instead of fullpath on validating authenticity token

PR #38211 introduced a bug where URLs with query_params
will fail to validate authenticity token.

This PR changes changes fullpath to path to fix the bug.
I've also added a test with query_params

Skip keeps option shouldn't restrict from creating empty directories

Allow schema cache path to be defined in the database configuration file

This updates the database tasks for dumping the Active Record schema cache as
well as clearing the schema cache file, allowing the path to be defined in the
database configuration YAML file.

As before, the value can also be defined in an ENV variable, though this would
not work for a multi-db application. If the value is specified neither in the
DB config, nor in the ENV, then the path will continue to be derived from the
DB config spec_name.

Note that in order to make this change cleaner I also moved a bit of logic
out of a rake task and into the DatabaseTasks class, for symmetry.

We have two rake tasks for the schema cache:

    $ rake db:schema:cache:dump
    $ rake db:schema:cache:clear

The cache:dump task was implemented in DatabaseTasks, but the
cache:clear one was not.

I also added some tests for the behavior that I was changing, since some of
the code paths weren't tested.

Update list of middleware for API-only in Guides

[ci skip]

[ci skip]

Deprecate `#remove_connection` in favor of `#remove_connection_pool`

Add Que backend to Active Job guide [ci skip]

Fix keyword arguments warnings in Active Job

Calling `#remove_connection` on the handler is deprecated in favor of
`#remove_connection_pool`. This change was made to support changing the
return value from a hash to a `DatabaseConfig` object.
`#remove_connection` will be removed in 6.2.

NOTE: `#remove_connection` on `ActiveRecord::Base` will also now return
a `DatabaseConfig` object. We didn't use a deprecation here since
it's not documented that this method used to return a `Hash`.
Co-authored-by: NJohn Crepezzi <john.crepezzi@gmail.com>

Closes #38276.

Use --assume-yes to install the dependencies for Github's workflows:

Add test for figcaption in actiontext

Fix doc code formatting [ci skip]

Fix syntax typo in changelog

Fix typo introduced in #38269