gistfile1.rb

      namespace :inquiries do
        resources :combiners, only: [:create]
      end
      
      # supervise_inquiries_combiners_path	
      # /supervise/inquiries/combiners                  ! нет :inquiry_id
      # supervise/inquiries/combiners#create 

      resources :inquiries do
        resources :combiners
      end
      
      # supervise_inquiry_combiners_path	
      # /supervise/inquiries/:inquiry_id/combiners	
      # supervise/combiners#create                      ! не тот контроллер
      
      resources :inquiries do
        scope module: :inquiries do
          resources :combiners
        end
      end
      
      # supervise_inquiry_combiners_path               путь нормальный
      # /supervise/inquiries/:inquiry_id/combiners     id есть
      # supervise/inquiries/combiners#create           контроллер верный