Andrey Demidenko

<%= email_field_tag(:email, nil, class: 'sub_mail' %>

descendant_ids Returns a list of a descendant ids

ActiveModelSerializers::SerializableResource.new(Partnership.where(partner_id: current_user.id, accepted: true), { each_serializer: PartnershipSerializer })

category = ["Комплектующие для ПК", "ПО", "ОС"]
ancestry = Category.find_or_create_by!(name: category.shift)
category.each do |value|
  ancestry = Category.find_or_create_by!(name: value, ancestry: ancestry)
end

Что касается использования AC и redis, то есть указание:

# Use Redis adapter to run Action Cable in production
# gem 'redis', '~> 3.0'