Add e-road and a-road for transportation z4. (#1619)

Adding [e-road](https://wiki.openstreetmap.org/wiki/WikiProject_Europe/E-road_network) and [AsianHighway](https://wiki.openstreetmap.org/wiki/Asia/Asian_Highway_Network) (as `a-road`) as part of the network to show up from zoom 4.

layers/transportation/network_type.sql

@@ -17,7 +17,9 @@ $$
                 'us-interstate', 'us-highway', 'us-state',
                 'ca-transcanada', 'ca-provincial-arterial', 'ca-provincial',
                 'gb-motorway', 'gb-trunk', 'gb-primary',
-                'ie-motorway', 'ie-national', 'ie-regional'
+                'ie-motorway', 'ie-national', 'ie-regional',
+                'e-road',
+                'a-road'
                 );
     END
 $$;
@@ -29,6 +31,11 @@ $$
         -- Canada
         'ca-transcanada', 'ca-provincial-arterial',
         -- United States
-        'us-interstate');
+        'us-interstate',
+        -- Europe
+        'e-road',
+        -- Asia
+        'a-road'
+    );
 $$ LANGUAGE sql IMMUTABLE
                 PARALLEL SAFE;

layers/transportation/update_route_member.sql

@@ -48,6 +48,11 @@ WHERE length(ref) > 1
 CREATE OR REPLACE FUNCTION osm_route_member_network_type(network text, ref text) RETURNS route_network_type AS
 $$
 SELECT CASE
+           -- https://wiki.openstreetmap.org/wiki/WikiProject_Europe/E-road_network
+           WHEN network = 'e-road' THEN 'e-road'::route_network_type
+           -- https://wiki.openstreetmap.org/wiki/Asia/Asian_Highway_Network
+           WHEN network = 'AsianHighway' THEN 'a-road'::route_network_type
+           -- https://wiki.openstreetmap.org/wiki/United_States_roads_tagging
            WHEN network = 'US:I' THEN 'us-interstate'::route_network_type
            WHEN network = 'US:US' THEN 'us-highway'::route_network_type
            WHEN network LIKE 'US:__' THEN 'us-state'::route_network_type