Support for additional authorization types

[jeremyowensboggs]

Currently, there is only shared key support. We also need support for SAS tokens and Managed Identities. What do you think that should look like?

1. Do we want to handle it all in config, so the call signatures stay the same?
2. add support for auth type in options?
3. a use Azurex, <options> approach?
4. other?

Thank You

[jakobht]

I don't think we should change the signatures. I think a combination of 2 and 3 would be great. Not sure how big of a change it is to support other auth?