Backfill centroid points for boundary relations

[1ec5]

openmaptiles/openmaptiles#1763 requests automatically backfilling a place=* point feature at the centroid of a boundary relation that lacks a label member, so that OSM doesn’t have to maintain manually positioned centroids for administrative boundaries representing partitions of other administrative boundaries. However, administrative boundaries representing populated places, such as villages, would continue to have manually positioned label members, so there would be no change for those. I wonder if this codebase might be able to implement something along these lines without breaking compatibility with the OpenMapTiles schema.

Planetiler would have to synthesize the required tags for the point based on the boundary relation’s tags. class=* would come from the relation’s place=* tag (as a temporary stopgap), falling back to border_type=*. For example, border_type=province would become province and border_type=county would become county.

This would make Planetiler more resilient to missing label nodes, since the place=* classification scheme can’t express every kind of partition anyways. It would also make Planetiler more resilient to vandalism that the OSM community is unable to catch promptly because OSM Carto doesn’t use these place points. For example, these vandalized place points for Egypt and Israel lasted two days and were only fixed after a Wikipedian spotted them on a Planetiler-based map:

Vandalism