Those are mini tasks still to do. They should be filed against a bug
trucker as soon as TPL will have one:

- use Private struct
- include Avatar token in logstore
- fix dbus_g_method_return_error
- use DBus TP spec and Co.
- use debug.c/h

- understand if TplContact is still useful or can be substitued by a
  simple TpContact
- use the Message interface of received messages to handle delivery
  notifications & Co.