Improve create-link error handling

internal/connectors/engine/engine.go

@@ -996,6 +996,9 @@ func (e *engine) CreatePaymentServiceUserLink(ctx context.Context, applicationNa
 	openBankingForwardedUser, err := e.storage.OpenBankingForwardedUserGet(ctx, psuID, connectorID)
 	if err != nil {
 		otel.RecordError(span, err)
+		if errors.Is(err, storage.ErrNotFound) {
+			return "", "", fmt.Errorf("payment service user has not been forwarded to connector '%s'. Please forward the payment service user to the connector before creating a link: %w", connectorID, ErrValidation)
+		}
 		return "", "", err
 	}
 
@@ -1089,6 +1092,9 @@ func (e *engine) UpdatePaymentServiceUserLink(ctx context.Context, applicationNa
 	openBankingForwardedUser, err := e.storage.OpenBankingForwardedUserGet(ctx, psuID, connectorID)
 	if err != nil {
 		otel.RecordError(span, err)
+		if errors.Is(err, storage.ErrNotFound) {
+			return "", "", fmt.Errorf("payment service user has not been forwarded to connector '%s'. Please forward the payment service user to the connector before updating a link: %w", connectorID, ErrValidation)
+		}
 		return "", "", err
 	}
 

internal/connectors/engine/engine_test.go

@@ -917,7 +917,8 @@ var _ = Describe("Engine Tests", func() {
 			store.EXPECT().OpenBankingForwardedUserGet(gomock.Any(), psuID, connectorID).Return(nil, storage.ErrNotFound)
 			_, _, err := eng.CreatePaymentServiceUserLink(ctx, "Test", psuID, connectorID, idempotencyKey, clientRedirectURL)
 			Expect(err).NotTo(BeNil())
-			Expect(err).To(MatchError(storage.ErrNotFound))
+			Expect(err).To(MatchError(ContainSubstring("payment service user has not been forwarded to connector")))
+			Expect(err).To(MatchError(ContainSubstring("Please forward the payment service user to the connector before creating a link")))
 		})
 
 		It("should return error when connection attempt upsert fails", func(ctx SpecContext) {
@@ -1045,7 +1046,8 @@ var _ = Describe("Engine Tests", func() {
 			store.EXPECT().OpenBankingForwardedUserGet(gomock.Any(), psuID, connectorID).Return(nil, storage.ErrNotFound)
 			_, _, err := eng.UpdatePaymentServiceUserLink(ctx, "Test", psuID, connectorID, connectionID, idempotencyKey, clientRedirectURL)
 			Expect(err).NotTo(BeNil())
-			Expect(err).To(MatchError(storage.ErrNotFound))
+			Expect(err).To(MatchError(ContainSubstring("payment service user has not been forwarded to connector")))
+			Expect(err).To(MatchError(ContainSubstring("Please forward the payment service user to the connector before updating a link")))
 		})
 
 		It("should return error when connection not found", func(ctx SpecContext) {

test/e2e/api_open_banking_test.go

@@ -139,6 +139,43 @@ var _ = Context("Payments API Open Banking", Serial, func() {
 		})
 	})
 
+	When("creating a link without forwarding PSU", func() {
+		var (
+			connectorID string
+		)
+
+		BeforeEach(func() {
+			var err error
+
+			id := uuid.New()
+			conf := newV3ConnectorConfigFn()(id)
+			conf.LinkFlowError = pointer.For(false)
+			conf.UpdateLinkFlowError = pointer.For(false)
+			connectorID, err = installV3Connector(ctx, app.GetValue(), conf, id)
+			Expect(err).To(BeNil())
+		})
+
+		AfterEach(func() {
+			uninstallConnector(ctx, app.GetValue(), connectorID)
+		})
+
+		It("should fail with clear error message when PSU has not been forwarded", func() {
+			applicationName := "test"
+			_, err := app.GetValue().SDK().Payments.V3.CreateLinkForPaymentServiceUser(
+				ctx,
+				psuID,
+				connectorID,
+				&components.V3PaymentServiceUserCreateLinkRequest{
+					ApplicationName:   &applicationName,
+					ClientRedirectURL: "https://www.google.com",
+				},
+			)
+			Expect(err).To(HaveOccurred())
+			Expect(err.Error()).To(ContainSubstring("payment service user has not been forwarded to connector"))
+			Expect(err.Error()).To(ContainSubstring("Please forward the payment service user to the connector before creating a link"))
+		})
+	})
+
 	When("creating a link and call it - success", func() {
 		var (
 			connectorID string