OAuth2 callback URL is now configurable

config/environments/production.rb

@@ -126,4 +126,7 @@ Rails.application.configure do
   # Any action dealing with authentication should redirect to HTTPS
   # Disabled because it will redirect incorrectly behind a proxy.
   # config.to_prepare { Devise::SessionsController.force_ssl }
+
+  # Needed (at least) for devise.rb to determine the oauth2 callback URL
+  config.base_url = ENV['DEBSHOTS_BASE_URL'] || 'http://localhost:3000'
 end