Underground layer=-5 metro platform is rendered over buildings

[martin-kokos]

Issue:
A metro platform highway=platform is rendered over the buildings although its layer is set to -5

Expected:
The platform should rendered below the buildings faded or with a dashed outline (similar to railway=subway), but also above layer like highway=pedestrian areas.

https://www.openstreetmap.org/way/487954656
https://www.openstreetmap.org/way/498558859

Related:
#3336
#2037
#3162

[dch0ph]

The correct tagging for underground platforms is location=underground. #3162 is a merged PR which addressed this (at least for platforms mapped as areas) rather than an open issue.