Add expand to allowed_params

Author: rydama

lib/stripe_mock/request_handlers/subscriptions.rb

@@ -106,7 +106,7 @@ def create_subscription(route, method_url, params, headers)
           customer[:default_source] = new_card[:id]
         end
 
-        allowed_params = %w(customer application_fee_percent coupon items metadata plan quantity source tax_percent trial_end trial_period_days current_period_start created prorate billing_cycle_anchor billing days_until_due idempotency_key enable_incomplete_payments cancel_at_period_end default_tax_rates payment_behavior pending_invoice_item_interval default_payment_method collection_method on_behalf_of transfer_data, expand)
+        allowed_params = %w(customer application_fee_percent coupon items metadata plan quantity source tax_percent trial_end trial_period_days current_period_start created prorate billing_cycle_anchor billing days_until_due idempotency_key enable_incomplete_payments cancel_at_period_end default_tax_rates payment_behavior pending_invoice_item_interval default_payment_method collection_method on_behalf_of transfer_data expand)
         unknown_params = params.keys - allowed_params.map(&:to_sym)
         if unknown_params.length > 0
           raise Stripe::InvalidRequestError.new("Received unknown parameter: #{unknown_params.join}", unknown_params.first.to_s, http_status: 400)