* Fix rdoc code formatting — `tt`, not backticks

* Fix/simplify sentence grammar — should at least just be “and the like”, not “likes”, but this is just general tightening up.

* Add note that delegated methods must be public.  Tested here: https://github.com/rails/rails/blob/7ff5ccae94ce2aff76b5f8a31a28e305a047d642/activesupport/test/core_ext/module_test.rb#L359-L365

* Simplify example code for delegate_missing_to. The example had complexity that wasn’t necessary for demonstrating `delegate_missing_to`.  This gets rid of a bunch of cruft so the example is more obvious about what’s going on regarding the feature itself.

[ci skip]

It's causing a test to fail, and we're not yet sure what (if anything)
we should be doing differently. See rubygems/rubygems#1911.

Move `package.json` creation to `create_root_files`

Since `package.json` is created in root directory, it is appropriate to
create it in `create_root_files`.

Fix to use correct path with language on guide

Use target language's document.yaml [ci skip]

Let me build guide with "ko" language,
    
    Before:
    - It try to use guides/source/documents.yaml
    
    After:
    - It try to use guides/source/ko/documents.yaml

Should test against `Relation#bound_attributes`

Since legacy `Relation#bind_values` was removed in b06f64c3.

Extract `bind_param` and `bind_attribute` into `ActiveRecord::TestCase`

Remove duplicated `test_merging_reorders_bind_params`

The same test exists in `test/cases/relation/merging_test.rb`.

https://github.com/rails/rails/blob/v5.1.0/activerecord/test/cases/relation/merging_test.rb#L94-L101

These are used in tests from anywhere.

fix ActiveModel::Validator#kind code examples

remove uniqueness validators from ActiveModel examples [ci-skip]

Add type caster to `RuntimeReflection#alias_name`

Since we have been using this `Arel::Table` since 111ccc83,
in order to properly handle queries, it's important that we properly type cast arguments.

Add missing require in ActionMailer::Base

Rails secrets is not built on but inspired by Sekrets

Put wording in line with http://weblog.rubyonrails.org/2017/4/27/Rails-5-1-final/

Without this, Action Mailer doesn't work like it used to on version 4.
The following snippet fails since version 5:

    > require 'action_mailer'
    > ActionMailer::Base
    NameError: uninitialized constant ActiveSupport::Rescuable

Deprecate `supports_statement_cache?`

Use `flat_map` rather than `map(&:...).flatten`

CLI arg `--port` has precedence over env `PORT`

Add tests for rendering with variants

Friendly maintain schema error in test runner

Update the Gem Bug Report Templates to 5.1.0

Remove unnecessary `package.json` deletion

5.1.0 has been released, and the gem templates can reflect that now.

The `package.json` is created only if `skip_yarn` is not specified.
https://github.com/rails/rails/blob/a4c1282854795d1f0d7696ce1ccbabf94b3d9098/railties/lib/rails/generators/rails/app/app_generator.rb#L202..L204

`supports_statement_cache?` was introduced in 3.1.0.beta1 (104d0b26) for
bind parameter substitution, but it is no longer used in 3.1.0.rc1
(73ff6797). Originally it should respect `prepared_statements` rather
than `supports_statement_cache?` (fd398475).
One more thing, named `supports_statement_cache?` is pretty misreading.
We have `StatementCache` and `StatementPool`. However,
`supports_statement_cache?` doesn't mean `StatementCache`, but
`StatementPool` unlike its name.

https://github.com/rails/rails/blob/v5.1.0/activerecord/lib/active_record/statement_cache.rb
https://github.com/rails/rails/blob/v5.1.0/activerecord/lib/active_record/connection_adapters/statement_pool.rb

The `:doc:` was added in bc478158 but originally `UriEncoder` is a
`:nodoc:` class.

[ci skip]

Merge pull request #28936 from dixpac/dixpac/update-docs-ActionDispatch__Journey__Router__Utils.unescape_uri

Add docs for  Router::Utils.unescape_uri method. [ci skip]

Fix note about `secrets.yml` [ci skip]