Made project use a callback provider to avoid letting almost the whole world on blank

nginx/default.conf

@@ -8,10 +8,27 @@ server {
 
     # Public API is x/y/z. try_files performs an internal lookup at z/x/y.png.
     location ~ ^/tiles/(?<tile_x>[0-9]+)/(?<tile_y>[0-9]+)/(?<tile_z>[0-9]+)$ {
-        try_files /tiles/$tile_z/$tile_x/$tile_y.png =404;
+        if ($request_method = OPTIONS) {
+            add_header Access-Control-Allow-Origin "*" always;
+            add_header Access-Control-Allow-Methods "GET, HEAD, OPTIONS" always;
+            add_header Access-Control-Allow-Headers "Origin, Range, Accept" always;
+            add_header Content-Length 0;
+            return 204;
+        }
+        try_files /tiles/$tile_z/$tile_x/$tile_y.png @callback_provider_tile;
         add_header Cache-Control "public, max-age=86400, stale-while-revalidate=604800" always;
+        add_header Access-Control-Allow-Origin "*" always;
+        add_header Access-Control-Allow-Methods "GET, HEAD, OPTIONS" always;
+        add_header Access-Control-Allow-Headers "Origin, Range, Accept" always;
     }
 
+    # A callback-provider base layer fills transparent edges when configured.
+    location ~ ^/base/(?<base_x>[0-9]+)/(?<base_y>[0-9]+)/(?<base_z>[0-9]+)$ {
+        try_files /__callback_provider_base__ @callback_provider_base;
+    }
+
+    include /etc/nginx/includes/callback-provider.conf;
+
     # metadata.json and internal z/x/y.png paths are intentionally not public.
     location / {
         return 404;