feat: support multiple tile URL templates for flat tile maps

[LonghiTW]

Add support for 'tile_urls' field in flat tile map services, allowing a single map layer to consist of multiple tile URL sources that are fetched and composited together.

• Make tile_url and tile_urls mutually exclusive (at least one required)
• Add UrlOption inner class and tileUrls field to TileMapServiceCommonProperties
• Update FlatTileMapService to download and composite images from multiple URLs
• Add Taiwan LiDAR Map as example with multi-year tile_urls in default_maps.yml

[LonghiTW]

I've reworked the PR based on Zoriot's feedback:

Single field, no dual-field support

You were right that keeping tile_url + tile_urls long-term is a terrible idea — so the tile_urls field is gone entirely. tile_url now accepts either one URL string or a list of URL strings, normalized internally into a List:

# single source (unchanged, backward compatible)
tile_url: https://example.com/{z}/{y}/{x}.png

# multiple sources
tile_url:
  - https://2024.example.com/{z}/{y}/{x}.png
  - https://2023.example.com/{z}/{y}/{x}.png

Existing configs keep working as-is, and serialization always writes back the single tile_url key (string for one source, array for multiple).

All commits are signed.

[Zoriot]

Blindly ignoring the exception without any explanation is not so nice

[Zoriot]

Seems to not work at all.

Show log

[15:59:47] [Render thread/INFO]: [System] [CHAT] T+- » Teleported to 25.014052, 121.463778, 11.
[15:59:49] [Render thread/INFO]: [FANCYMENU] ScreenCustomizationLayer registered: pause_screen
[15:59:49] [Render thread/INFO]: Resized a dynamic immediate buffer to 160!
[15:59:49] [Render thread/INFO]: Resized a dynamic immediate buffer to 320!
[15:59:49] [Render thread/INFO]: Resized a dynamic immediate buffer to 640!
[15:59:49] [Render thread/INFO]: Resized a dynamic immediate buffer to 1280!
[15:59:50] [Render thread/INFO]: [FANCYMENU] ScreenCustomizationLayer registered: com.mndk.bteterrarenderer.mcconnector.client.gui.screen.AbstractGuiScreenImpl
[15:59:50] [terra++ disk I/O thread/INFO]: [STDOUT]: [2026/08/09 15:59:50:260] INFO [terra++ bootstrap] Cache miss: https://www.historygis.udd.gov.taipei/urban/assets/images/logo.svg
[15:59:53] [terra++ disk I/O thread/INFO]: [STDOUT]: [2026/08/09 15:59:53:507] INFO [terra++ bootstrap] Cache miss: https://maps.nlsc.gov.tw/images/entrance.gif
[15:59:54] [terra++ HTTP network thread/INFO]: [STDOUT]: [2026/08/09 15:59:54:808] INFO [terra++ bootstrap] Request succeeded: https://maps.nlsc.gov.tw/images/entrance.gif
[16:00:00] [terra++ HTTP network thread/INFO]: [STDOUT]: [2026/08/09 16:00:00:653] INFO [terra++ bootstrap] Request succeeded: https://www.historygis.udd.gov.taipei/urban/assets/images/logo.svg
[16:00:00] [ForkJoinPool.commonPool-worker-1/ERROR]: Error processing cache value
java.util.concurrent.CompletionException: java.lang.RuntimeException: com.mndk.bteterrarenderer.dep.batik.transcoder.TranscoderException: null
Enclosed Exception:
null:0
The URI "data:image/png;base64,
<printed data of the file>
on element <image> can't be opened because:
URL data in unsupported format or corrupt
	at knot//com.mndk.bteterrarenderer.dep.batik.bridge.UserAgentAdapter.getBrokenLinkDocument(UserAgentAdapter.java:448)

[Zoriot]

Tests are failing for me.

Show log

Can not write a field name, expecting a value
com.fasterxml.jackson.core.JsonGenerationException: Can not write a field name, expecting a value
	at com.fasterxml.jackson.core.JsonGenerator._reportError(JsonGenerator.java:2733)
	at com.fasterxml.jackson.core.json.WriterBasedJsonGenerator.writeFieldName(WriterBasedJsonGenerator.java:153)
	at com.fasterxml.jackson.core.JsonGenerator.writeObjectField(JsonGenerator.java:2407)
	at com.mndk.bteterrarenderer.core.tile.TileMapServiceCommonProperties.write(TileMapServiceCommonProperties.java:102)
	at com.mndk.bteterrarenderer.core.tile.TileMapServiceCommonPropertiesTest.writeJson(TileMapServiceCommonPropertiesTest.java:72)
	at com.mndk.bteterrarenderer.core.tile.TileMapServiceCommonPropertiesTest.givenMultipleTileUrls_whenWriteCalled_thenWrittenAsArray(TileMapServiceCommonPropertiesTest.java:64)