Part of Apartment with no subdomain

apartment.rb

require 'apartment/elevators/generic'

Apartment.configure do |config|
  # Your Customer model
  config.excluded_models = %w{ Customer }

  # Customer name will be the key of the tenant
  config.tenant_names = lambda { Customer.pluck :name }
end

Rails.application.config.middleware.use Apartment::Elevators::Generic, lambda { |request|
  request.session[:tenant] ? request.session[:tenant] : 'public'
}