Fix loading Stripe invoices

Broken since the recent refactoring. Need to now call `id` on the Stripe
Customer object and pass this into the list invoices API call.

Fixes #8465

app/models/alaveteli_pro/invoice_collection.rb

@@ -52,7 +52,7 @@ def each(&block)
     def invoices
       return [] unless @customer
 
-      @invoices ||= Stripe::Invoice.list(customer: @customer)
+      @invoices ||= Stripe::Invoice.list(customer: @customer.id)
     end
   end
 end

spec/models/alaveteli_pro/invoice_collection_spec.rb

@@ -3,7 +3,7 @@
 
 RSpec.describe AlaveteliPro::InvoiceCollection do
   let(:collection) { described_class.new(customer) }
-  let(:customer) { double(:customer) }
+  let(:customer) { double(:customer, id: 'cus_123') }
 
   let(:open_invoice) { double(:invoice, status: 'open') }
   let(:paid_invoice) { double(:invoice, status: 'paid', amount_paid: 10) }
@@ -39,7 +39,7 @@
       let(:invoices) { Stripe::ListObject.new }
 
       before do
-        allow(Stripe::Invoice).to receive(:list).with(customer: customer).
+        allow(Stripe::Invoice).to receive(:list).with(customer: 'cus_123').
           and_return(invoices)
       end
 
@@ -55,7 +55,7 @@
 
   describe '#open' do
     before do
-      allow(Stripe::Invoice).to receive(:list).with(customer: customer).
+      allow(Stripe::Invoice).to receive(:list).with(customer: 'cus_123').
         and_return([open_invoice, paid_invoice])
     end
 
@@ -66,7 +66,7 @@
 
   describe '#paid' do
     before do
-      allow(Stripe::Invoice).to receive(:list).with(customer: customer).
+      allow(Stripe::Invoice).to receive(:list).with(customer: 'cus_123').
         and_return([open_invoice, paid_invoice])
     end
 
@@ -88,7 +88,7 @@
       let(:invoices) { Stripe::ListObject.new }
 
       before do
-        allow(Stripe::Invoice).to receive(:list).with(customer: customer).
+        allow(Stripe::Invoice).to receive(:list).with(customer: 'cus_123').
           and_return(invoices)
         allow(invoices).to receive(:auto_paging_each).
           and_yield(open_invoice).
@@ -106,7 +106,7 @@
 
     context 'without Stripe invoices' do
       before do
-        allow(Stripe::Invoice).to receive(:list).with(customer: customer).
+        allow(Stripe::Invoice).to receive(:list).with(customer: 'cus_123').
           and_return([open_invoice, paid_invoice, open_invoice])
       end