public static Geometry combineLineStrings(List<LineString> lineStrings) {
    return lineStrings.size() == 1 ? lineStrings.getFirst() : createMultiLineString(lineStrings);
  }
More aggressive fix for self-intersections than {@link #fixPolygon(Geometry)} that expands then contracts the shape
by {@code buffer}.

@throws GeometryException if a robustness error occurred
planetiler-core/src/main/java/com/onthegomap/planetiler/geo/GeoUtils.java