[tor-relays] tor prometheus metrics -> expected label value, got "INVALID"

[Fran]

Hej David,

> Thanks for reporting and investigating!! :)

Thank you for fixing and implementing in the first place!

Really looking forward to see some nice graphs showing how many
people use our services via onion.

BTW: Implementation of nusenu feature request[1] for exposing more relay 
health metrics for prometheus would be awesome! :)

Best,
fran

[1] https://gitlab.torproject.org/tpo/core/tor/-/issues/40194