multi: make canceled invoice garbage collection configurable

This commit extends the application config with a flag to control canceled
invoice garbage collection upon startup.

invoices/invoiceregistry.go

@@ -57,6 +57,10 @@ type RegistryConfig struct {
 	// send payments.
 	AcceptKeySend bool
 
+	// GcCanceledInvoicesOnStartup if set, we'll attempt to garbage collect
+	// all canceled invoices upon start.
+	GcCanceledInvoicesOnStartup bool
+
 	// KeysendHoldTime indicates for how long we want to accept and hold
 	// spontaneous keysend payments.
 	KeysendHoldTime time.Duration
@@ -171,7 +175,9 @@ func (i *InvoiceRegistry) scanInvoicesOnStart() error {
 
 		if invoice.IsPending() {
 			pending[paymentHash] = invoice
-		} else if invoice.State == channeldb.ContractCanceled {
+		} else if i.cfg.GcCanceledInvoicesOnStartup &&
+			invoice.State == channeldb.ContractCanceled {
+
 			// Consider invoice for removal if it is already
 			// canceled. Invoices that are expired but not yet
 			// canceled, will be queued up for cancellation after

invoices/invoiceregistry_test.go

@@ -1091,8 +1091,9 @@ func TestOldInvoiceRemovalOnStart(t *testing.T) {
 	require.NoError(t, err)
 
 	cfg := RegistryConfig{
-		FinalCltvRejectDelta: testFinalCltvRejectDelta,
-		Clock:                testClock,
+		FinalCltvRejectDelta:        testFinalCltvRejectDelta,
+		Clock:                       testClock,
+		GcCanceledInvoicesOnStartup: true,
 	}
 
 	expiryWatcher := NewInvoiceExpiryWatcher(cfg.Clock)