Decouple transport layer

[rexm]

The Transport layer is currently more tightly coupled than I'd like. Top improvements:

• Completely decouple from Net / WebRequest
• Abstract the AWS Authentication mechanism and make that testable stand-alone

[chandu]

@rexm Can you pls elaborate on the decoupling part?
One way I can think of is using the System.Net.Http.HttpClient for the http communication and it is more testable.
At some level you need a component making the web calls.

[rexm]

I welcome suggestions! The individual pieces-parts at the REST layer and WebRequest layer don't feel right. That's about all I've got right now :) I like the HttpClient idea... Good start.

[chandu]

@rexm Started working on using HttpClient for the rest communication.
Can you take a look at commit d4c5302 on my branch refactor-transport and let me know if you see any issues with the approach?

@rexm @chandu Hey, just to make sure we're not duplicating work, I am implementing issue #4 - Provide async implementation of API which utilizes HttpClient. To see iteration 1 of my implementation please see 8269fd6. It is only the first iteration, but all of the tests are passing for the async implementation. Next step I think will be to remove the dependency on the entity framework...

[rexm]

Thanks for weighing in @rbeauchamp-lendingtree. My impression is your work starts from HttpClient-up and @chandu's is going HttpClient-down. If we can keep that as the only overlap, reconciling it should be pretty easy. Let me know if you see more risk than that...

Sure. Sounds fine.