The following extended metrics information are exposed through
the debug API:
- last seen timestamp - updated every time when the peer
connects/disconnects
- connection total duration - sums of the duration of the sessions
  (in seconds)
- session connection retry count - number of attempts to create
  a new connection
- session connection duration - duration (in seconds) of last or
  current (if in progress) session
- session connection direction - specifies whether the connection is
  outbound or inbound