Generalize API Integration Description within the API Declaration

[freeformflow]

We should have a field specifying what a given GW method integrates with:

1. A Lamdba published in the publish command
2. A Lambda that is pulbished some other time (via a different runtime even)
3. A non-Lambda AWS service
4. or simply a proxy to another interface.

This has to be balanced with the desire to make the Sky API decription generic, not assuming the use a particular Cloud Platform. One possible means to do that is via a API Description Extension. We can create an integration field, and that can be an AnyOf of Description Extensions sub-schemas, currently only AWS's API Gateway

However, @automatthew is concerned that this risks being to constrictive.

Okay, here's an idea why we shouldn't do that.

What if you want to use someone else's packaged API Description and lambda handlers, but you need to override some part of the integration?
This is so murky right now that I think we should find a way to punt on it. Maybe a separate file for integration mapping.

@dyoder has suggested the usage of a pragma as a temporary measure while we finalize the design.