Function prepare_resubmission_aux_data 

pub fn prepare_resubmission_aux_data<Block: BlockT>(
    block_hash: Block::Hash,
    proof: Arc<StorageProof>,
    relay_parent_header: Header,
    relay_parent_session: SessionIndex,
) -> impl Iterator<Item = (Vec<u8>, Vec<u8>)>

Build the aux-data key/value pairs to commit alongside a block.

The caller should push these into BlockImportParams::auxiliary so they commit in the same DB transaction as the block. Stateless — no backend access required.