Document feasibility of using RADOS to ensure seamless flow OIDC with Ceph/S3 Rucio Storage Element

Context: In Rucio, the only storage element with a seamless flow with the OIDC authentication is storm/webdav (as inferred from the last Rucio Workshop). There is no such full integration of the OIDC authentication with others Rucio Storage Endpoints (RSEs) based in other resource management system like dCache or S3.

At the same time, RADOS gateway facilitates the integration between OIDC and Ceph/S3 (see see: https://softiron.com/blog/integrating-rados-gateway-with-an-external-oidc-provider/ and Ceph: https://docs.ceph.com/en/quincy/radosgw/index.html)

The aim of this feature is to explore how to use RADOS gateway in order to support a seamless integration of the OIDC authentication with RSE based in Ceph/S3.