Add support for AMP and zero amount invoices

Author: thomasbarrett

lightning_client.go

@@ -1390,6 +1390,7 @@ func (s *lightningClient) AddInvoice(ctx context.Context,
 		Expiry:          in.Expiry,
 		CltvExpiry:      in.CltvExpiry,
 		Private:         true,
+		IsAmp:           in.Amp,
 	}
 
 	if in.Preimage != nil {

router_client.go

@@ -379,6 +379,7 @@ func (r *routerClient) SendPayment(ctx context.Context,
 		MaxParts:         request.MaxParts,
 		OutgoingChanIds:  request.OutgoingChanIds,
 		AllowSelfPayment: request.AllowSelfPayment,
+		Amt:              int64(request.Amount),
 	}
 	if request.MaxCltv != nil {
 		rpcReq.CltvLimit = *request.MaxCltv
@@ -415,7 +416,6 @@ func (r *routerClient) SendPayment(ctx context.Context,
 	// payment parameters.
 	if request.Invoice == "" {
 		rpcReq.Dest = request.Target[:]
-		rpcReq.Amt = int64(request.Amount)
 		rpcReq.PaymentHash = request.PaymentHash[:]
 		rpcReq.FinalCltvDelta = int32(request.FinalCLTVDelta)