AWS S3 in CAS proxy

[migmartri]

The CAS proxy is a layer in front of different CAS backends. At the moment of this writing only OCI repositories are supported.

THe goal of this task is to

• Allow the artifact CAS proxy to be able to support more than 1 provider (OCI, S3) at the same time
• The specific provider (OCI, S3) could be selected on the fly in each request, so in addition to receiving the credentials reference now it will also receive the backend type.
• Implement AWS s3 blob storage CAS backend

[danlishka]

What if we first add support for AWS S3 and then we will tackle a way to have a CAS proxy? Or we need to do both at the same time?

[migmartri]

What if we first add support for AWS S3 and then we will tackle a way to have a CAS proxy? Or we need to do both at the same time?

We discussed this offline and there was a misunderstanding. The scope of this issue is not to change how Chainloop attestation process uses the CAS, but the internal implementation of the cas-proxy. How it could handle requests for different backends.