When a model nests another model that also nests yet another model
using accepts_nested_attributes_for method, its Errors object can
have an attribute name with "contacts.addresses.street" style.
In this case, the dots within the namespace should be substituted
with slashes so that we can provide the translation under the
"activemodel.attributes.person/contacts/addresses.street" key.
This commit is related to #3859.
Nested I18n namespace lookup under activerecord.models is deprecated now (c19bd4f).
But when a model uses accepts_nested_attributes_for, its Errors object can have
an attribute name with "addresses.street" style. In this case, the dots should be
substituted with slashes so that we can provide the translation under the
"activemodel.attributes.person.addresses/street" key.
For example, you could easily specify :created_at and :updated_at translations as:
en:
attributes:
created_at: "Created at"
updated_at: "Updated at"
This configuration is built on ActiveModel, so it means those translations are
shared between different ORMs as well (but always as a fallback).
