User Delegation SAS URL Builder

@vincenttran-msft @jalauzon-msft

Ref #3330

I started writing a crate for user delegation sas urls that I'd like to upstream here. I also left a comment with some context in the issue references above, but didn't hear back. @heaths suggested opening an issue to discuss it more, maybe you already have some idea of what it would look like. I just used the ms learn docs to get something up and running using a builder pattern focused on preventing improper url generation, since the docs are kind of all over the place in terms of categorization of optional headers, parameters and so on.

Any feedback is welcomed, I just want to get something up and running so I can ship my service this week. I think it's already pretty close to something I'd expect to see API wise, and the generated docs are pretty clear in pointing out where to find things in the ms learn docs.

https://github.com/eureka-cpu/azure-storage-sas