Support S3 read-only IAM user roles

I want to setup research environments to have read-only access to the S3 account containing our databases. However, it looks like quantrocket db s3config checks for create bucket permissions to validate the configuration, which shouldn’t be necessary for QR installations that will only be using s3pull.

I agree, read-only should be supported here.

Read-only users are supported in version 2.3.0.