Expand explanation of how to set secrets.yml. [ci skip]
Merge pull request #14654 from Alamoz/secret_key

Expand explanation of how to set secrets.yml.
depend_on_asset is not required anymore on sprockets-rails 2.1.2
Add missing require so requiring `active_support/cache` works again.
Merge pull request #14667 from lucasmazza/require-per-thread-registry

Add missing require so requiring `active_support/cache` works again.
Avoid URI parsing

This parsing is unecessary once the Request object already has the
needed information.
Merge pull request #14665 from andrielfn/avoid-uri-parsing

Avoid URI parsing