bug(PastUsage) - Filter fees by external subscription id (#2723)

## Context

Past usage endpoint allows you to retrieve past usage, an external
subscription id parameter is required.
However, we incorrectly send all fees belonging to the found invoice, we
should filter these by the subscription id as well.

app/queries/past_usage_query.rb

@@ -41,7 +41,7 @@ def query
   end
 
   def fees_query(invoice)
-    query = invoice.fees.charge.includes(:charge_filter)
+    query = invoice.fees.joins(:subscription).where(subscription: {external_id: filters.external_subscription_id}).charge.includes(:charge_filter)
     return query unless filters.billable_metric_code
 
     query.joins(:charge).where(charges: {billable_metric_id: billable_metric.id})

spec/queries/past_usage_query_spec.rb

@@ -17,6 +17,7 @@
   let(:customer) { create(:customer, organization:) }
   let(:plan) { create(:plan, organization:) }
   let(:subscription) { create(:subscription, customer:, plan:) }
+  let(:subscription2) { create(:subscription, customer:, plan:) }
 
   let(:invoice_subscription1) do
     create(
@@ -36,6 +37,15 @@
     )
   end
 
+  let(:invoice_subscription3) do
+    create(
+      :invoice_subscription,
+      charges_from_datetime: DateTime.parse('2023-07-17T00:00:00'),
+      charges_to_datetime: DateTime.parse('2023-08-16T23:59:59'),
+      subscription: subscription2
+    )
+  end
+
   before do
     invoice_subscription1
     invoice_subscription2
@@ -107,6 +117,43 @@
       end
     end
 
+    context 'with fees belonging to multiple subscriptions' do
+      let(:billable_metric1) { create(:billable_metric, organization:) }
+      let(:billable_metric_code) { billable_metric1&.code }
+
+      let(:billable_metric2) { create(:billable_metric, organization:) }
+
+      let(:charge1) { create(:standard_charge, plan:, billable_metric: billable_metric1) }
+      let(:charge2) { create(:standard_charge, plan:, billable_metric: billable_metric2) }
+
+      let(:fee1) { create(:charge_fee, charge: charge1, subscription:, invoice: invoice_subscription1.invoice) }
+      let(:fee2) { create(:charge_fee, charge: charge2, subscription: subscription2, invoice: invoice_subscription1.invoice) }
+
+      let(:filters) do
+        {
+          external_customer_id: customer.external_id,
+          external_subscription_id: subscription.external_id
+        }
+      end
+
+      before do
+        invoice_subscription3
+        fee1
+        fee2
+      end
+
+      it 'filters the fees accordingly' do
+        result = usage_query.call
+
+        aggregate_failures do
+          expect(result).to be_success
+          expect(result.usage_periods.count).to eq(2)
+          expect(result.usage_periods.first.fees.count).to eq(1)
+          expect(result.usage_periods.first.fees.first.subscription).to eq(subscription)
+        end
+      end
+    end
+
     context 'with billable_metric_code' do
       let(:billable_metric1) { create(:billable_metric, organization:) }
       let(:billable_metric_code) { billable_metric1&.code }
@@ -116,8 +163,8 @@
       let(:charge1) { create(:standard_charge, plan:, billable_metric: billable_metric1) }
       let(:charge2) { create(:standard_charge, plan:, billable_metric: billable_metric2) }
 
-      let(:fee1) { create(:charge_fee, charge: charge1, invoice: invoice_subscription1.invoice) }
-      let(:fee2) { create(:charge_fee, charge: charge2, invoice: invoice_subscription1.invoice) }
+      let(:fee1) { create(:charge_fee, charge: charge1, subscription:, invoice: invoice_subscription1.invoice) }
+      let(:fee2) { create(:charge_fee, charge: charge2, subscription:, invoice: invoice_subscription1.invoice) }
 
       let(:filters) do
         {

spec/requests/api/v1/customers/usage_controller_spec.rb

@@ -351,8 +351,8 @@
 
     let(:invoice) { invoice_subscription.invoice }
 
-    let(:fee1) { create(:charge_fee, charge: charge1, invoice:) }
-    let(:fee2) { create(:charge_fee, charge: charge2, invoice:) }
+    let(:fee1) { create(:charge_fee, charge: charge1, subscription:, invoice:) }
+    let(:fee2) { create(:charge_fee, charge: charge2, subscription:, invoice:) }
 
     let(:path) do
       [