Read a sender's LinkedIn connection

Returns whether a LinkedIn account is connected to this sender, and if so its live state: which browsers are connected and when each was last seen, today's usage against each ceiling, how much work is queued, and what the next step waits on and until when (the time between steps, a limit's reset). Not-connected is a normal state rather than a 404: it carries the connection token the person pastes into the extension, and reading it is what mints that token.