[Tagging] Proposed feature - electricity

[Marc_marc]

> Would signed_origin be clear enough?

signed/web/local knowledge/opendata is a source.
I see no advantage to create a prefix for every key for every source.
source key exist for that.

> I want to make clear that we are tagging advertised claims, 

if a restaurant displays in its window that it does vegan cuisine, it is
also advertised claims as long as I have not been eaten there and check
that the fat used in the kitchen is of vegetable origin and check bills
to see if he buy enough vegan fat.
fortunately no one called for the creation of the suffix :advertised for
cuisine and diet

>> you can verify when something is open by checking it sufficiently often.

you can, of course, but did you do that ?
you add opening_hours only by checking yourself every day of the week at
what time it opens and closes ? this is certainly not what the majority
of contributors do. so the majority of opening_hours are
advertised claims.
did you also check contract for every POI with diet:vegan ?
almost everyone add claims in osm, even when doing something as simple
as adding addr:housenumber (2 signs have been switched, the sign for the
number on the building is an claim, this is not the truth).

>> I a also dubious about usefulness of mapping this

a well known closed-data app have this info.
in countries where part of the grid's electricity comes from coal,
I understand that some users want to choose a less polluting poi.