Create a main entrypoint class

[moltar]

Problem

As we have an example: https://github.com/ScaleLeap/amazon-advertising-api-sdk#api-operations

There are too many steps to get started quickly.

Solution

Ideally we should have a main class, something like AmazonAdvertising that accepts:

• Marketplace object
• Auth

And creates all of the moving parts internally, exposing a simple and clean API.

We still want to export the internals, just in case as stand-alone classes.

But the main use case would be via the entry point class.

Please create a proposal / PoC for this class.

[nguyentoanit]

@moltar: I have created a proposal for this class in PR #354. Thanks.