Support access to S3 storage using Service account role

Currently, while configuring the S3 as only storage for the Pulp in eks, the only way to provide access for pods to s3 is through access keys specified in a k8 secret.
I did give a try with giving necessary permissions to a service account role to access s3, and attaching that service account role arn to the pods using spec.sa_annotations option in Pulp CR . But the pulp cr always expects spec.object_storage_s3_secret. Thus wasnt able to use only the service account option (without a s3 secret) with pulpcr. Could this support be added to the Pulp CR, so that access key as secret can be avoided. Especially when the pulp deployment is taken care using git, the storing of the access keys in git is slightly challenging, and cant be fully automated.

Raising this issue, based on the discussion in https://discourse.pulpproject.org/t/how-to-install-pulp-on-aws-eks-cluster-with-s3-storage/893/34

Start at the Pulp CR handling of spec.object_storage_s3_secret and spec.sa_annotations, tracing where S3 credentials are required. Review the linked Discourse discussion for the intended service-account-only configuration. Done means a Pulp CR can use the service account role without an S3 secret while retaining the existing secret-based option.