support fully qualified column names in properties and filter query parameters

[iferencik]

pg_tileserv supports combining 2 tables in one request but the properties or filter query parameters accept only relative/simple names not the fully qualified names of columns.

https://pgtileserv.undpgeohub.org/admin.admin0/{z}/{x}/{y}.pbf?filter=perimeter_km=3000 AND continent='AFR'

supporting fully qualified column names and allowing referencing the geometry column would open the door to something like this

https://pgtileserv.undpgeohub.org/admin.admin0,infrastructure.roads/{z}/{x}/{y}.pbf?filter=INTERSECTS(admin.admin0.geom, insfrastructure.roads.geom ) AND infrastructure.roads.surface_type='asphalt'

thanks