So this trick is not needed to be documented anymore.

This was also removed from #15542

Add a config to setup whether raise exception for missing translation or
not.

default_formats array is used by LookupContext in order to allow
rendering templates when :formats option is not passed. Previously it
was always set to Mime::SET, which created dependency on Action Pack. In
order to remove this dependency, Mime::SET is used only if
ActionController is loaded.

I've talked to José Valim, who added this comment, and there is no need
to remove old API. It's good to have a simple way to instantiate
ActionView::Base, by just passing view paths as a first argument,
instead of constructing LookupContext and then the Renderer.

[ci skip]

remove AV.prepare and move all helper-related logic into the controller. this decouples the view since it no longer knows about routes internals.
this is a result of an ongoing discussion at https://github.com/rails/rails/pull/6826.

config.action_view.prefix_partial_path_with_controller_namespace

This allows you to choose to render @post using
/posts/_post.erb instead of /admin/posts/_post.erb
inside Admin::PostsController.

uses PATCH for the forms of persisted records, and routes PATCH and PUT to the update action of resources

PATCH is the correct HTML verb to map to the #update action. The
semantics for PATCH allows for partial updates, whereas PUT requires a
complete replacement.

Changes:
* adds config.default_method_for_update you can set to :patch
* optionally use PATCH instead of PUT in resource routes and forms
* adds the #patch verb to routes to detect PATCH requests
* adds #patch? to Request
* changes documentation and comments to indicate support for PATCH

This change maintains complete backwards compatibility by keeping :put
as the default for config.default_method_for_update.