fix(stripe): pass idempotency key for charge intents

lib/mpp/methods/stripe/charge_intent.rb

@@ -60,7 +60,10 @@ def verify(credential, request)
 
           begin
             client = ::Stripe::StripeClient.new(@secret_key)
-            result = client.v1.payment_intents.create(params)
+            result = client.v1.payment_intents.create(
+              params,
+              {idempotency_key: stripe_idempotency_key(credential)}
+            )
           rescue => e
             raise Mpp::VerificationError, e.message
           end
@@ -84,6 +87,12 @@ def verify(credential, request)
 
           Mpp::Receipt.success(pi_id, method: "stripe", external_id: external_id)
         end
+
+        private
+
+        def stripe_idempotency_key(credential)
+          "mpp-stripe-charge-#{credential.challenge.id}"
+        end
       end
     end
   end

test/mpp/methods/stripe/test_charge_intent.rb

@@ -75,7 +75,11 @@ def test_verify_calls_stripe_sdk
 
     mock_result = Struct.new(:id, :status).new("pi_abc123", "succeeded")
     mock_pi = Minitest::Mock.new
-    mock_pi.expect(:create, mock_result, [Hash])
+    mock_pi.expect(:create, mock_result) do |params, opts|
+      assert_equal 100, params[:amount]
+      assert_equal "usd", params[:currency]
+      assert_equal "mpp-stripe-charge-test-id", opts[:idempotency_key]
+    end
 
     mock_v1 = Struct.new(:payment_intents).new(mock_pi)
     mock_client = Struct.new(:v1).new(mock_v1)
@@ -123,7 +127,7 @@ def test_verify_rejects_replayed_payment
     mock_last_response = Struct.new(:headers).new(mock_headers)
     mock_result = Struct.new(:id, :status, :last_response).new("pi_abc123", "succeeded", mock_last_response)
     mock_pi = Minitest::Mock.new
-    mock_pi.expect(:create, mock_result, [Hash])
+    mock_pi.expect(:create, mock_result, [Hash, {idempotency_key: "mpp-stripe-charge-test-id"}])
 
     mock_v1 = Struct.new(:payment_intents).new(mock_pi)
     mock_client = Struct.new(:v1).new(mock_v1)
@@ -144,7 +148,7 @@ def test_verify_rejects_requires_action
 
     mock_result = Struct.new(:id, :status).new("pi_needs3ds", "requires_action")
     mock_pi = Minitest::Mock.new
-    mock_pi.expect(:create, mock_result, [Hash])
+    mock_pi.expect(:create, mock_result, [Hash, {idempotency_key: "mpp-stripe-charge-test-id"}])
 
     mock_v1 = Struct.new(:payment_intents).new(mock_pi)
     mock_client = Struct.new(:v1).new(mock_v1)