@Override
    boolean isMetadataChunk() {
      return true;
    }
Initialize the MetadataPutChunk.
If {@link RouterConfig#routerReservedMetadataEnabled} is {@code true}, then this will initialize the reserved
metadata chunk id. There are three cases:
1. If this is a chunked upload, then the reserved metadata chunk id is passed in the blob properties.
2. If this is a stitched blob request, then the reserved metadata is obtained from the specified chunksToStitch.
3. If this is a regular upload, then a new reserved metadata chunk id is generated. Note that this reserved metadata
   id will be used only for composite blobs.

@param chunksToStitch {@link List} of {@link ChunkInfo} objects to stitch for a stitchBlob request.
                      Will be {@code null} for all other put requests.
@throws RouterException In case of any error.
ambry-router/src/main/java/com/github/ambry/router/PutOperation.java