Improve establish session duration metrics
Before we took into account the time a user takes to authenticate. Now it only measures the time between a connection established and a command started to being executed.
It still can be controlled by a user: for example, if a user implements its own SSH client and waits infinitely before sending session commands. But it's something we can measure and restrict if necessary.
Related issue: #583 (closed)
Edited by Igor Drozdov