Vector tile feature ID method (#960)

planetiler-core/src/main/java/com/onthegomap/planetiler/reader/osm/OsmElement.java

@@ -235,4 +235,13 @@ public interface OsmElement extends WithTags {
   record Info(long changeset, long timestamp, int userId, int version, String user) {
     private static final int COST = 2;
   }
+
+  static long vectorTileFeatureId(int multiplier, long id, Type type) {
+    return (id * multiplier) + switch (type) {
+      case OTHER -> 0;
+      case NODE -> 1;
+      case WAY -> 2;
+      case RELATION -> 3;
+    };
+  }
 }

planetiler-core/src/main/java/com/onthegomap/planetiler/reader/osm/OsmReader.java

@@ -646,12 +646,7 @@ public class OsmReader implements Closeable, MemoryEstimator.HasEstimate {
 
     @Override
     public long vectorTileFeatureId(int multiplier) {
-      return (id() * multiplier) + switch (originalElement.type()) {
-        case OTHER -> 0;
-        case NODE -> 1;
-        case WAY -> 2;
-        case RELATION -> 3;
-      };
+      return OsmElement.vectorTileFeatureId(multiplier, id(), originalElement.type());
     }
 
     @Override

planetiler-core/src/main/java/com/onthegomap/planetiler/reader/osm/OsmRelationInfo.java

@@ -15,4 +15,8 @@ public interface OsmRelationInfo extends MemoryEstimator.HasEstimate {
   default long estimateMemoryUsageBytes() {
     return 0;
   }
+
+  default long vectorTileFeatureId(int multiplier) {
+    return OsmElement.vectorTileFeatureId(multiplier, id(), OsmElement.Type.RELATION);
+  }
 }