Add aboriginal lands (#1489)

This PR adds support for `boundary=aboriginal_lands` by adding it to the `park` layer. While these lands are certainly not "parks", they have similar treatment from a technology perspective and can benefit from the existing processing chain established in that layer. I set all of these objects to `class=aboriginal_lands` in the tiles, including at the lowest zoom in order to separate it from the protected area merging implemented in #1160. In order to distinguish these from general parks, I expose the `class` attribute for these objects at z4 and also ensure that the z4 generalization is performed separately for protected areas versus aboriginal lands.

This unblocks #ZeLonewolf/openstreetmap-americana#105, which describes why having indigenous land boundaries is an important general feature on the map. This is also consistent with my suggested implementation in https://github.com/openmaptiles/openmaptiles/issues/1296#issuecomment-967749403.

layers/park/mapping.yaml

@@ -101,3 +101,4 @@ tables:
       boundary:
       - national_park
       - protected_area
+      - aboriginal_lands

layers/park/park.sql

@@ -26,11 +26,12 @@ SELECT osm_id,
 FROM (
          SELECT osm_id,
                 geometry,
-                COALESCE(
-                        LOWER(REPLACE(NULLIF(protection_title, ''), ' ', '_')),
-                        NULLIF(boundary, ''),
-                        NULLIF(leisure, '')
-                    ) AS class,
+                CASE WHEN boundary='aboriginal_lands' THEN 'aboriginal_lands'
+                     ELSE COALESCE(
+                          LOWER(REPLACE(NULLIF(protection_title, ''), ' ', '_')),
+                          NULLIF(boundary, ''),
+                          NULLIF(leisure, '')
+                    ) END AS class,
                 name,
                 name_en,
                 name_de,
@@ -45,7 +46,7 @@ FROM (
                          NULL AS name_de,
                          NULL AS tags,
                          NULL AS leisure,
-                         NULL AS boundary,
+                         CASE WHEN boundary='aboriginal_lands' THEN boundary END AS boundary,
                          NULL AS protection_title
                   FROM osm_park_polygon_dissolve_z4
                   WHERE zoom_level = 4

layers/park/park.yaml

@@ -17,6 +17,7 @@ layer:
           `nature_reserve` is the class of `protection_title=Nature Reserve` and `leisure=nature_reserve`.
           The class for other [`protection_title`](http://wiki.openstreetmap.org/wiki/key:protection_title) 
           values is similarly assigned.
+          The class for `boundary=aboriginal_lands` is `aboriginal_lands`.
     name: The OSM [`name`](http://wiki.openstreetmap.org/wiki/Key:name) value of the park (point features only).
     name_en: English name `name:en` if available, otherwise `name` (point features only).
     name_de: German name `name:de` if available, otherwise `name` or `name:en` (point features only).

layers/park/update_park_polygon.sql

@@ -24,14 +24,16 @@ DROP MATERIALIZED VIEW IF EXISTS osm_park_polygon_dissolve_z4 CASCADE;
 CREATE MATERIALIZED VIEW osm_park_polygon_dissolve_z4 AS
 (
   SELECT min(osm_id) AS osm_id,
-         ST_Union(geometry) AS geometry
+         ST_Union(geometry) AS geometry,
+         boundary
   FROM (
         SELECT ST_ClusterDBSCAN(geometry, 0, 1) OVER() AS cluster,
                osm_id,
-               geometry
+               geometry,
+               boundary
         FROM osm_park_polygon_gen_z4
   ) park_cluster
-  GROUP BY cluster
+  GROUP BY boundary, cluster
 );
 CREATE UNIQUE INDEX IF NOT EXISTS osm_park_polygon_dissolve_idx ON osm_park_polygon_dissolve_z4 (osm_id);