invoicesrpc: add SubscribeSingleInvoice rpc

lnrpc/invoicesrpc/config_active.go

@@ -3,7 +3,9 @@
 package invoicesrpc
 
 import (
+	"github.com/btcsuite/btcd/chaincfg"
 	"github.com/lightningnetwork/lnd/invoices"
+	"github.com/lightningnetwork/lnd/macaroons"
 )
 
 // Config is the primary configuration struct for the invoices RPC server. It
@@ -12,5 +14,19 @@ import (
 // configuration options, while if able to be populated, the latter fields MUST
 // also be specified.
 type Config struct {
+	// NetworkDir is the main network directory wherein the invoices rpc
+	// server will find the macaroon named DefaultInvoicesMacFilename.
+	NetworkDir string
+
+	// MacService is the main macaroon service that we'll use to handle
+	// authentication for the invoices rpc server.
+	MacService *macaroons.Service
+
+	// InvoiceRegistry is a central registry of all the outstanding invoices
+	// created by the daemon.
 	InvoiceRegistry *invoices.InvoiceRegistry
+
+	// ChainParams are required to properly decode invoice payment requests
+	// that are marshalled over rpc.
+	ChainParams *chaincfg.Params
 }