Function find_preprint_doi 

pub async fn find_preprint_doi(
    doi: &Doi,
    crossref_message: &Value,
    biorxiv_enabled: bool,
    ctx: &FetchContext,
) -> Result<Option<FoundDoi>, FetchError>

Look for a non-arXiv preprint of doi (#640): Crossref’s relation, then bioRxiv and medRxiv pubs when biorxiv_enabled.

Errors

A provenance-log failure only; a request that fails is a finder that found nothing.