Avoid repeated refreshes for persisted async invoices

lightning/src/ln/async_payments_tests.rs

@@ -2450,6 +2450,25 @@ fn refresh_static_invoices_for_used_offers() {
 		.handle_onion_message(server.node.get_our_node_id(), &invoice_persisted_om);
 	assert_eq!(recipient.node.flow.test_get_async_receive_offers().len(), 1);
 
+	// The invoice was just refreshed and persisted. A later timer tick must wait until the next
+	// refresh threshold before generating another invoice for the same offer.
+	recipient.node.timer_tick_occurred();
+	let pending_oms_after = recipient.onion_messenger.release_pending_msgs();
+	let mut extra_serve_invoices = 0;
+	if let Some(msgs) = pending_oms_after.get(&server.node.get_our_node_id()) {
+		for msg in msgs {
+			if let PeeledOnion::AsyncPayments(AsyncPaymentsMessage::ServeStaticInvoice(_), _, _) =
+				server.onion_messenger.peel_onion_message(&msg).unwrap()
+			{
+				extra_serve_invoices += 1;
+			}
+		}
+	}
+	assert_eq!(
+		extra_serve_invoices, 0,
+		"used offer invoice was refreshed again immediately after a successful refresh"
+	);
+
 	// Remove the peer restriction added above.
 	server.message_router.peers_override.lock().unwrap().clear();
 	recipient.message_router.peers_override.lock().unwrap().clear();

lightning/src/offers/async_receive_offer_cache.rs

@@ -491,7 +491,7 @@ impl AsyncReceiveOfferCache {
 			match offer.status {
 				OfferStatus::Used { invoice_created_at: ref mut inv_created_at }
 				| OfferStatus::Ready { invoice_created_at: ref mut inv_created_at } => {
-					*inv_created_at = core::cmp::min(invoice_created_at, *inv_created_at);
+					*inv_created_at = core::cmp::max(invoice_created_at, *inv_created_at);
 				},
 				OfferStatus::Pending => offer.status = OfferStatus::Ready { invoice_created_at },
 			}