Currently, when we serialize and compress events for archiving, json.gz files are dumped to the local filesystem and then manually rotated to external storage that is not publicly available. We got the go ahead to share these archives, so we should move the existing archives to the publicly-readable object store used in {T386475}.
Most of our existing archives use an old schema that is incompatible with our current ORM. So we should migrate those before publication.
**Acceptance criteria:**
[] Previous archives use current event object schema
[] Archives hosted in a publicly readable object store
[] Archives have a predictable / logical path that allows for easy bulk download based on date without needing to interrogate an api or scrape any web pages; this should be in alignment with T386475