[Feature Request] Outlines of administrative entities in the "network map"

[StC-OSM]

When you are doing QA analyses of networks in France, you sometimes need to ask yourself if the connections between networks are at the right place. In 95% of cases this boils down to comparing the network to the outline of an administrative level: more or less, we have one network per intermunicipality.

Therefore it would be great if the "network map" view could show the outlines of administrative levels. If I dared, I'd also ask for "Parcs Nationaux" and "Parcs Naturels Régionaux". Experience shows that in most places, intermunicipalities delegate route management to parks, and we need to assign nodes and route relations to park networks rather than intermunicipality networks. However, I don't what would be the meaningful equivalent in other countries than France.

[vmarc]

To show all relevant boundaries in the knooppuntnet maps will require an additional vector based map tile set containing these boundaries.

The background vector tiles that are generated with OpenMapTiles already contain some of the boundaries, but not all the boundary levels that we need.

The location map page currently shows the boundary of that specific location. This is realized by loading the boundary information from the server in geojson format for that particular location. To do a similar thing for all location boundaries will not scale from performance point of view. When we have an additional boundary tile set, this could also be used to highlight individual boundaries (based on boundary osm relation id), and the geojson download will not be needed anymore. Not sure if that would allow to colour the area within the boundary (as done now in the location map page), or only the outline of the boundary.