Invalid HTTP method will raise I18n::InvalidLocale if :en is not a valid locale.

Request#check_method would use to_sentence(locale: :en), which breaks when
I18n.available_locales does not include :en and
I18n.enforce_available_locales is true (default).

Inlined to_sentence functionality to solve this.

[ci skip] removing ruby-i18n.org/wiki link that is not available and usi...

[ci skip] removing ruby-i18n.org/wiki link that is not available and using “gems” instead of plugins

Don't pass retry option to Sidekiq

* This would override whatever default is configured in Sidekiq
  system-wide, and retry is true by default anyway.

update error message when InlineAdapter is used

Warning about middleware not auto-reloading

Add a section in the guide to explain that Rails can't auto-reload
a middleware on code change.

Fix #16806

[ci skip]

fix tests on action_mailer

Include appropriate helpers and use `assert_dom_equal` where applicable

remove un-needed sort

HTML doesn't care what order the elements are rendered in, so why should we?

Updates tests to use proper `assert_dom_equal` instead of `assert_equal` /cc @jeremy

Fix grammar [ci skip]

Rephrasing sentences

fix autoload tests

Change `gsub` to `tr` where possible

update queue_classic details [ci skip]

Fix typo in Active Model guide

- instrospection -> introspection.
- [ci skip]

Merge branch 'active-model-secure-password-guide' of https://github.com/aditya-kapoor/rails into aditya-kapoor-active-model-secure-password-guide

Conflicts:
	guides/source/active_model_basics.md

- Some grammatical errors and rewording of sentences throughout document

- Renaming headers to be more human readable, and if following paragraphs do not include module
  names, adding those in

- In ActiveModel::AttributeMethods
  * formatting expected output correctly, changing from `#` to `# =>`

- In ActiveModel::Dirty
  * changing expected output of person.first_name_was from "First Name" to nil
  * removing 'active_model' requirement at top of code snippet

- In ActiveModel::Validations
  * originally Person.new(token: "2b1f325") raises an argument error (1 for 0), so setting of
    attribute occurs on the line after object instantiation

- In ActiveModel::Naming
  * closing code snippet tag at end of section so ActiveModel::Model is a separate section

- In ActiveModel::Model
  * fixing spelling mistake of attr_accessor

- In ActiveModel::Serialization
  * adding edit to description of how from_json and from_xml works under serialization

- In ActiveModel::Lint::Tests
  * capitalizing person for class name

[ci skip] Clarify deletion strategies for collection proxies

doc added for `writer` method in `alias_method_chain` [ci skip]

For detailed testing of behavior see:
https://gist.github.com/eileencodes/5b0a2fe011dcff6203fe

This shows destroy_all always destroys records and fires callbacks.
It will never use nullify or delete_all

delete_all's behavior varies greatly based on `hm` vs `hm:t` and deletion
strategy.

in the database. Closes #16304 [ci skip]

Docs: Add a note on custom validation contexts. [ci skip]

Fix underscore inflector handling of namespaced and adjacent acronyms