Support file uploads

This allows submissions to store file uploads

config/initializers/host.rb

@@ -0,0 +1 @@
+DEFAULT_HOST = ENV['DEFAULT_HOST'] || 'localhost:3000'

config/routes.rb

@@ -4,7 +4,10 @@ Rails.application.routes.draw do
   resources :forms do
     resources :submissions
   end
+  # short link for submission file uploads
+  get '/s/:form_id/:submission_id/:id' => 'file_uploads#show', as: :file_upload
 
+  # form post url to save new submissions
   post '/s/:form_id' => 'submissions#create', as: :submission
 
   get '/login' => 'sessions#new', as: :login