Allow role based authentication

My feature is not pretty, but assuming the roles are set up with the correct trust policy, this works!

Thanks for the MR! I've been wanting to do this. I'll give it a review in the next day or so.

I think it can probably do with a bit of a refactor. As-is it will request new temporary credentials each time it makes an API call, but the temporary credentials it receives are (by default) valid for an hour, so it shouldn't need to.

Thanks, it looks good to me. Merged!

Automatically closed - issue fixed for 2 weeks with no activity.