Bring back feature that allows loading external route files:

= This feature existed back in 2012 https://github.com/rails/rails/commit/5e7d6bba79393de0279917f93b82f3b7b176f4b5
  but got reverted with the incentive that there was a better approach.
  After discussions, we agreed that it's a useful feature for apps
  that have a really large set of routes.
Co-authored-by: NYehuda Katz <wycats@gmail.com>

I added myself links to the Ruby on Rails Tutorial years ago, after
meeting Michael in a RailsConf.

By then, the book was a commercial product, but had a free online
version and I thought it could be a good resource complementing the
official documentation.

Nowadays, only a few sample chapters are available for free, and I
don't consider these links to be fair with the rest of commercial
books about Rails anymore.

Revert "Use `app.config.file_watcher` for watcher in `RoutesReloader`"

This reverts commit 28e44f47.

A limitation of Listen is that it currently only supports watching directories.
Therefore, watching `config/routes.rb` will end up watching the entire `config` directory
if we use the evented file watcher. This causes problems especially if symlinks are present
in the `config` directory.

system tests: properly set driver options for non-headless drivers

Use `app.config.file_watcher` for watcher in `RoutesReloader`

Upgrade listen to 3.2.1 for darwin fixes

Pulls in a fix where the darwin adapter no longers create a `fsevent_watch` process
for each directory that Listen has been asked to watch.

Closes #37666

Don't parse DB specific locking docs as code

[ci skip]

Add guide for inline around_action

This reverts commit 5bbb2a65, reversing
changes made to f9e4906c.

Reason: Since #36866, we use `azure-storage-blob` gem. So the original
description is correct.

Small doc fixes for ActiveJob::Exceptions::ClassMethods#retry_on

[ci skip]

Should keep the original parts for zero duration

Follow up to https://github.com/rails/rails/pull/31872

Particularly, the closing `</tt>` tag of the documented wait algorithm had a misplaced `<`.  Threw in a space between `15% (0.15)` for good measure.

[ci skip]

Add support for conditional values to TagBuilder

Distinguish missing controller exceptions from unrelated NameError

Update active_storage_overview.md

Deprecate `database` kwarg from `connected_to` without replacement

Remove deprecated non-symbol access to nested config_for hashes

Fix: https://github.com/rails/rails/issues/37650

The classic autoloader used to totally unregister any constant that
failed midway. Which mean `"SomeConst".constantize` was idempotent.

However Zeitwerk rely on normal `Kernel#require` behavior, which mean
that if an exception is raised during a class/module definition,
it will be left incompletely defined. For instance:

```ruby
class FooController
  ::DoesNotExist

  def index
  end
end
```

Will leave `FooController` defined, but without its `index` method.

Because of this, when silencing a NameError, it's important
to make sure the missing constant is really the one we were trying
to load.

in initializer block to the selenium driver
for non-headless browsers

* refactored browser options initialization.
* improved method names in AD::SystemTesting::Browser
* improved AD::SystemTest driver tests

Follow up to https://github.com/rails/rails/pull/37849#issuecomment-560557239.

Without this, `0.days` is considered as `0.seconds` due to #31310.
We should not lose the original parts.

Hide internal utility methods in the public API doc [ci skip]

[skip ci] Update initialization guide start method to include change

I digged the history for the internal utility methods (`convert_key`,
`convert_value`, and `set_defaults`), I believe it is apparently not
intended to appear them in the public API doc.

* `convert_key`, `convert_value`: 71742114
* `set_defaults`: #20828

https://api.rubyonrails.org/v6.0.1/classes/ActiveSupport/HashWithIndifferentAccess.html

Since we sometimes makes breaking change for internal methods (e.g.
#37870), so that methods should not be leaked to the public API doc.

Fix bug in configs_for

The `database` kwarg in `connected_to` has resulted in a lot of bug
reports that are trying to use it for sharding when that's not the
intent of the key. After considering where the database kwarg is used in
tests and thinking about usecases for it, we've determined it should be
removed.

There are plans to add sharding support and in the mean time the
database kwarg isn't the right solution for that. Applications that need
to create new connections can use establish_connection or connects_to.
Since the database key causes new connections to be established on every
call, that causes bugs if connected_to with a database kwarg is used
during a request or for any connection that's not a one-off.
Co-authored-by: NJohn Crepezzi <john.crepezzi@gmail.com>

If a spec name was provided without an env name, config_for would return
the first config that matched the spec, regardless of environment name.

Now configs_for will return the database config that matches the
default env and requested spec name.

Additionally this commit has moved the default env call into a method
because I'm tired of typing so many lines every single time.

We considered either returning all configs that match that spec name or
raising an error if only spec was passed, but this change has the least
impact on current behavior and matches Active Record's assumptions: that
if you ask for configs it will always consider the current environment.
Co-authored-by: NJohn Crepezzi <john.crepezzi@gmail.com>