lnrpc: report invoice state

Expose the new invoice state field over rpc.

rpcserver.go

@@ -3305,6 +3305,16 @@ func createRPCInvoice(invoice *channeldb.Invoice) (*lnrpc.Invoice, error) {
 
 	isSettled := invoice.Terms.State == channeldb.ContractSettled
 
+	var state lnrpc.Invoice_InvoiceState
+	switch invoice.Terms.State {
+	case channeldb.ContractOpen:
+		state = lnrpc.Invoice_OPEN
+	case channeldb.ContractSettled:
+		state = lnrpc.Invoice_SETTLED
+	default:
+		return nil, fmt.Errorf("unknown invoice state")
+	}
+
 	return &lnrpc.Invoice{
 		Memo:            string(invoice.Memo[:]),
 		Receipt:         invoice.Receipt[:],
@@ -3326,6 +3336,7 @@ func createRPCInvoice(invoice *channeldb.Invoice) (*lnrpc.Invoice, error) {
 		AmtPaidSat:      int64(satAmtPaid),
 		AmtPaidMsat:     int64(invoice.AmtPaid),
 		AmtPaid:         int64(invoice.AmtPaid),
+		State:           state,
 	}, nil
 }