Bearer token support

[joepio]

We currently support Cookies and HTTP signed headers, but not bearer tokens. @AlexMikhalev has a good usecase for this. Should not be hard to implement.

[AlexMikhalev]

An example of a use case: is dynamic config, where the Atomic Data server acts like a config server:
https://github.com/mehcode/config-rs/blob/6de19be2b5be7aa16b697c2587a04445c47defba/examples/async_source/main.rs
Needs nested queries unwrapping atomic resources.