Add full scaffold generator support

[jamesconant]

This issue is a (choose one):

• Feature request.

Checklist before submitting:

• I've searched for an existing issue.
• The feature I'm asking for is compliant with the JSON:API spec.

Description

Features:

note: this issue (or something similar to it) was brought up by @eccegordo in #1241. I opened this issue because I did not want to automatically close his in case our requests diverged, but will follow up with that issue if this issue is resolved with my PR.

As a developer, I need to be able to spin up new services, collect feedback, and validate those proofs-of-concepts as quickly as possible. Any time I spend writing boilerplate code is time not spent working on real value-adding features or concepts.

As such, I would like a way to quickly, consistently, and safely generate all of the required base file structures to get a jsonapi resource/endpoint working. Further, I would like these generated files to be opinionated, and help me fall into a "pit of success" / good practices.

In scope:

• generate (flat or name-spaced) base controllers
• generate (flat or name-spaced) controllers
• generate (flat or name-spaced) base resources
• generate (flat or name-spaced) resources
• generate (flat or name-spaced) base models
• generate (flat or name-spaced) models
• generate (flat or name-spaced) routes

Out of scope:

• declare attributes, associations, or other defining characteristics during generation
• parameterized generation options (e.g. "don't generate base classes")
• generate (flat or name-spaced) tests (future PR)