Add initial GitHub integration

[hwine]

Propose a squash merge on this -- or I can reorder & clean up some for a real review.

This branch is already running in jenkins staging without issues. All changes (except as noted) are in the github/ directory, so do not impact other code.

Changes outside of github/ are:

• Makefile - re-introduction of python version cross check (can be reverted), and some refactoring of finding all python files (could be improved)
• conftest.py - added in GitHub client, enhanced metadata handling as discussed
• setup.py - fix for document generation error
• tox.ini - added, but not used in Makefile yet, so can be reverted
• cache.py, service_report_generator.py, aws/* (2 files), gcp/* (1 file) - impact of running pyupgrade in my tree, single line syntax change, can be reverted
• adding bandit to pre-commit checks, with baseline for the one false positive it found
• adding other hygiene checks to pre-commit which all pass
• updated secrets baseline, as we no longer have false positives under docs/_build

[hwine]

I really think that some tests should be added, as there is a lot of code here. As well, there are a lot of TODO

So, this the tension between "land early incomplete, but not buggy" and "wait until it's perfect". The longer it live outside of the production branch, the more cruft may show up. We can discuss.

Also, what exactly is the github/github_schema.py file?

Ah, yes -- that is an autogenerated file by a tool in the graphQL library. Anytime we want to use a newer feature of the GitHub GraphQL API, we need to regenerate this file. That clearly needs some docs, but we don't want to regenerate it at packaging time, as we need a full test suite run.

To clarify the status of the code - it runs, and produces correct output which is stored for metrics usage. It does not yet consume the frost results and take actions. Think of it as the MVP, with more sprints to come.

We can discuss how we handle all this at the frost meetup

[hwine]

Also, what exactly is the github/github_schema.py file?

That clearly needs some docs, ...

Updated github/README.md in next commit