code: public OsmLayer createOsmLayer(String id, int nrOfLevels, String... urls) {
  		OsmLayer layer = new OsmLayer(id, createOsmTileConfiguration(nrOfLevels));
  		layer.addUrls(Arrays.asList(urls));
  		return layer;
  	}
docs: Create a new OSM layer with URLs to OSM tile services.
  <p/>
  The URLs should have placeholders for the x- and y-coordinate and tile level in the form of {x}, {y}, {z}.
  The file extension of the tiles should be part of the URL.
  
  @param id   The unique ID of the layer.
  @param conf The tile configuration.
  @param urls The URL to the tile services.
  @return A new OSM layer.
  @since 2.2.1