Data mirroring

[hannes-ucsc]

We would like the ability for Azul to manage a mirror in AWS of most/all of the data file in a source that it indexes. A source is a TDR snapshot, for example. When a client requests a file from the /repository/files endpoint, Azul should respond with a signed URL of the mirrored file, if it exists. Manifests, especially the curl manifest should also use the mirror.

The mirroring should be done for all sources in a catalog.

Currently, the most pressing use case is mirroring HCA in AWS.

Design: https://docs.google.com/document/d/197_hBqv9f3RP9Crr6ISI3G0JjEECDVyrIlKICpruL1A/edit?tab=t.0