transformer key should only be used on nodes

[francois.lacombe]

Dear maintainers,

JOSM currently warns when power=transformer is used on a way/area/relation.
It's not effective with transformer=* key which is restricted to nodes as well.
​https://wiki.openstreetmap.org/wiki/Key:transformer

For instance, a closed perimeter with power=substation + transformer=* should at least raise a warning about transformer=* key not used on a node.

This hasn't be part of #15367 and #12386

Thanks in advance for any fix

François

[skyper]

Please, do not set milestones. thanks.

[Klumbumbus]

In 17387/josm:

fix #20193 - Warn about transformer=* on ways