Docker entrypoint: authentication for Azure Blob

[christophkreutzer]

When using s3proxy as a proxy for S3 -> Azure Blob Storage, one needs to set the authentication parameters. When running in a container, these can be exposed via environment variables, but are currently not passed through to the jclouds config.

This is how we got it running for us in a custom build of the container.
Should I also add the options for other backends? Or do you see options for a generic solution?

Maybe also corresponds to #404

[gaul]

Thank you for your contribution @christophkreutzer! I am happy to add configs as one-offs but if there is some better mechanism please suggest it.

[christophkreutzer]

Hello @gaul, thanks for merging. I have no clear idea about a generic implementation, at least with env variables.

Another way would be allow passing a properties file (which could be Docker file mount or a configmap mount on Kubernetes), but that's a bit less elegant to use in my opinion.