Follow-up from "Upload offline exports directly to configured object storage"

The following discussion from !221351 (merged) should be addressed:

• @SamWord started a discussion: (+3 comments)

  Thought (non-blocking): It'd be nice if there could be one place where this identifier format is defined so that this module and the metadata service can share it. Non-blocking because I'm not really sure how to do that at the moment and the implementations of each are quite different