Add monitoring for IU Reference DOI TSV file

[yuanzhou]

11/07/2024 Summary of IU DOI Reference Redirection incident:

• Bruce rebuilt HRA KG but it didn't regenerate the reference TSV file
• Bruce generated the file and it's available again at https://cdn.humanatlas.io/digital-objects/reference-entity-ids.tsv
• But entity-api still failed to read the file
• Found out the Memcached cached the 404 response from earlier
• Cleared cache and that fixed the issue

Will add monitoring to the tsv file to fill the gap when the actual TSV is missing but entity-api still uses the cached result.