invoicesrpc: add HTLC modifier to invoices RPC server

This commit integrates the HTLC modifier service into the
invoices RPC server.

lnd.go

@@ -638,6 +638,7 @@ func Main(cfg *Config, lisCfg ListenerCfg, implCfg *ImplementationCfg,
 	err = rpcServer.addDeps(
 		server, interceptorChain.MacaroonService(), cfg.SubRPCServers,
 		atplManager, server.invoices, tower, multiAcceptor,
+		server.invoiceHtlcModifier,
 	)
 	if err != nil {
 		return mkErr("unable to add deps to RPC server: %v", err)