invoices: integrate settlement interceptor with invoice registry

This commit updates the invoice registry to utilize the settlement
interceptor during the invoice settlement routine. It allows the
interceptor to capture the invoice, providing interception clients an
opportunity to determine the settlement outcome.

htlcswitch/mock.go

@@ -1014,6 +1014,7 @@ func newMockRegistry(minDelta uint32) *mockInvoiceRegistry {
 		panic(err)
 	}
 
+	modifierMock := &invoices.MockHtlcModifier{}
 	registry := invoices.NewRegistry(
 		cdb,
 		invoices.NewInvoiceExpiryWatcher(
@@ -1022,6 +1023,7 @@ func newMockRegistry(minDelta uint32) *mockInvoiceRegistry {
 		),
 		&invoices.RegistryConfig{
 			FinalCltvRejectDelta: 5,
+			HtlcInterceptor:      modifierMock,
 		},
 	)
 	registry.Start()