Update Rust client SDK quickstart for 1.0 API (#162)

* Begin revising rust client quickstart: update the code

* Revise Rust client SDK quickstart

A whole bunch of stuff has changed since this document was last updated.
Notably, I've chosen to re-order a bunch of sections,
since the previous structure of the document doesn't make much sense
after the 0.12 API rework.

* Fix credentials import issue

There are still warnings here but it builds now

* Fix warnings after pasting all this code into a fresh project

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Co-authored-by: John Detter <[email protected]>

Author: gefjon