Build StackInABoxService based on OpenAPI

[BenjamenMeyer]

OpenAPI (aka Swagger) provides a rigid documentation on how an API is suppose to work. It may be helpful to provide the capability to take an OpenAPI specification and generate a StackInABoxService that can be used.

For reference, here's an example of doing the same thing for a live Flask app - https://connexion.readthedocs.io/en/latest/

Question: should this be part of StackInABox proper like the various utility integrations are? Or should it be its own project under the TestInABox org, similar to https://github.com/TestInABox/OpenStackInABox?

NOTE: There is no issue with providing utility integrations or StackInABoxService generators as separate projects, especially if dependencies to support are going to have hard requirements.

Leaving this here to track discussion.