Move aboriginal lands boundaries to boundary layer (#1604)

This PR adds indigenous lands to the `boundary` layer by adding new area features for these objects, along with generalization up to z4. It borrows heavily from the technical processing chain of the `park` layer.

I added new `class`, `name`, and `name:xx` attributes to the boundary layer, in order to support the new area features. Should we (or someone extending this schema) come up with new objects to place in the boundary layer in the future, `class` would support additional categories.

layers/park/mapping.yaml

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

layers/park/park.sql

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

layers/park/park.yaml

@@ -5,15 +5,11 @@ layer:
     such as parks tagged with [`boundary=national_park`](https://wiki.openstreetmap.org/wiki/Tag:boundary%3Dnational_park),
     [`boundary=protected_area`](https://wiki.openstreetmap.org/wiki/Tag:boundary%3Dprotected_area),
     or [`leisure=nature_reserve`](https://wiki.openstreetmap.org/wiki/Tag:leisure%3Dnature_reserve).
-    This layer also includes boundaries for indigenous lands tagged with 
-    [`boundary=aboriginal_lands`](https://wiki.openstreetmap.org/wiki/Tag:boundary%3Daboriginal_lands).
-    Indigenous boundaries are not parks, but they are included in this layer for technical reasons related to data processing.
-    These boundaries represent areas with special legal and administrative status for indigenous peoples.
   buffer_size: 4
   fields:
     class:
       description: |
-        Use the **class** to differentiate between different kinds of features in the `parks` layer, for example between parks and non-parks.
+        Use the **class** to differentiate between different kinds of features in the `parks` layer.
         The class for `boundary=protected_area` parks is the lower-case of the
         [`protection_title`](http://wiki.openstreetmap.org/wiki/key:protection_title)
         value with blanks replaced by `_`.
@@ -21,7 +17,6 @@ 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). Language-specific values are in `name:xx`.
     name_en: English name `name:en` if available, otherwise `name` (point features only). This is deprecated and will be removed in a future release in favor of `name:en`.
     name_de: German name `name:de` if available, otherwise `name` or `name:en` (point features only). This is deprecated and will be removed in a future release in favor of `name:de`.