lndclient: rename payment request expiry field

DecodePayReq reports expiry as a duration from the invoice timestamp,
while PaymentRequest exposes the computed absolute time. Rename Expiry
to ExpiresAt to make that semantic explicit.

This is a breaking API change: callers must update references from
PaymentRequest.Expiry to PaymentRequest.ExpiresAt. The rename prevents
existing callers from silently interpreting the changed value semantics.

Author: starius

lightning_client.go

@@ -2908,8 +2908,8 @@ type PaymentRequest struct {
 	// Timestamp of the payment request.
 	Timestamp time.Time
 
-	// Expiry is the time at which the payment request expires.
-	Expiry time.Time
+	// ExpiresAt is the time at which the payment request expires.
+	ExpiresAt time.Time
 
 	// Description is a description attached to the payment request.
 	Description string
@@ -2963,7 +2963,7 @@ func (s *lightningClient) DecodePaymentRequest(ctx context.Context,
 	if resp.Expiry != 0 {
 		// LND reports expiry as a duration from the invoice timestamp.
 		invoiceTimestamp := time.Unix(resp.Timestamp, 0)
-		paymentReq.Expiry = invoiceTimestamp.Add(
+		paymentReq.ExpiresAt = invoiceTimestamp.Add(
 			time.Duration(resp.Expiry) * time.Second,
 		)
 	}

lightning_client_test.go

@@ -37,9 +37,9 @@ func (m *mockDecodePayReqRPCClient) DecodePayReq(_ context.Context,
 	return m.response, nil
 }
 
-// TestLightningClientDecodePaymentRequestExpiry ensures that the relative
+// TestLightningClientDecodePaymentRequestExpiresAt ensures that the relative
 // expiry returned by lnd is converted to an absolute expiration time.
-func TestLightningClientDecodePaymentRequestExpiry(t *testing.T) {
+func TestLightningClientDecodePaymentRequestExpiresAt(t *testing.T) {
 	t.Parallel()
 
 	timestamp := time.Unix(1_700_000_000, 0)
@@ -65,7 +65,7 @@ func TestLightningClientDecodePaymentRequestExpiry(t *testing.T) {
 	require.NoError(t, err)
 	require.Equal(t, encoded, mock.request.PayReq)
 	require.Equal(t, timestamp, request.Timestamp)
-	require.Equal(t, timestamp.Add(expiry), request.Expiry)
+	require.Equal(t, timestamp.Add(expiry), request.ExpiresAt)
 }
 
 // mockRPCClient implements lnrpc.LightningClient with dynamic method