invoicesrpc: create sub server

Sub server implementation is still empty. This is a preparatory
step for adding invoice functionality.

subrpcserver_config.go

@@ -5,8 +5,10 @@ import (
 	"reflect"
 
 	"github.com/lightningnetwork/lnd/autopilot"
+	"github.com/lightningnetwork/lnd/invoices"
 	"github.com/lightningnetwork/lnd/lnrpc/autopilotrpc"
 	"github.com/lightningnetwork/lnd/lnrpc/chainrpc"
+	"github.com/lightningnetwork/lnd/lnrpc/invoicesrpc"
 	"github.com/lightningnetwork/lnd/lnrpc/signrpc"
 	"github.com/lightningnetwork/lnd/lnrpc/walletrpc"
 	"github.com/lightningnetwork/lnd/macaroons"
@@ -37,6 +39,10 @@ type subRPCServerConfigs struct {
 	// client to be notified of certain on-chain events (new blocks,
 	// confirmations, spends).
 	ChainRPC *chainrpc.Config `group:"chainrpc" namespace:"chainrpc"`
+
+	// InvoicesRPC is a sub-RPC server that exposes invoice related methods
+	// as a gRPC service.
+	InvoicesRPC *invoicesrpc.Config `group:"invoicesrpc" namespace:"invoicesrpc"`
 }
 
 // PopulateDependencies attempts to iterate through all the sub-server configs
@@ -47,7 +53,8 @@ type subRPCServerConfigs struct {
 // FetchConfig method.
 func (s *subRPCServerConfigs) PopulateDependencies(cc *chainControl,
 	networkDir string, macService *macaroons.Service,
-	atpl *autopilot.Manager) error {
+	atpl *autopilot.Manager,
+	invoiceRegistry *invoices.InvoiceRegistry) error {
 
 	// First, we'll use reflect to obtain a version of the config struct
 	// that allows us to programmatically inspect its fields.
@@ -125,6 +132,13 @@ func (s *subRPCServerConfigs) PopulateDependencies(cc *chainControl,
 				reflect.ValueOf(cc.chainNotifier),
 			)
 
+		case *invoicesrpc.Config:
+			subCfgValue := extractReflectValue(cfg)
+
+			subCfgValue.FieldByName("InvoiceRegistry").Set(
+				reflect.ValueOf(invoiceRegistry),
+			)
+
 		default:
 			return fmt.Errorf("unknown field: %v, %T", fieldName,
 				cfg)