ER log external power failure

From JuniperClue

The cases where all the powers of the router failed simultaneously (e.g., external power loss) and the router just simply rebooted/crashed without a trace are not distinguishable.

It would be very useful to be able to distinguish these, for example, by ensuring that there is always a trace of external power failure.

That way one could pinpoint the problem with certainty to either the router crashing or external power failure.