htlcswitch+server: add new field SelfKey to htlcswitch.Config

This commit adds a new field to the switch’s Config, namely the public
key of the backing lightning node. This field will soon be used to
return more detailed errors messages back to the ChannelRouter itself.

server.go

@@ -176,6 +176,7 @@ func newServer(listenAddrs []string, chanDB *channeldb.DB, cc *chainControl,
 	}
 
 	s.htlcSwitch = htlcswitch.New(htlcswitch.Config{
+		SelfKey: s.identityPriv.PubKey(),
 		LocalChannelClose: func(pubKey []byte,
 			request *htlcswitch.ChanClose) {