GitHub annotations: provide more output

[danwallach]

The autograders from GitHub Education all use the check_run facility to set annotations on the build. We should do this with the final score of the autograder.

Relevant code:

• Does the annotations. https://github.com/education/autograding/blob/master/src/output.ts
• Tests the annotations. https://github.com/education/autograding/blob/master/src/__tests__/output.test.ts

Relevant GitHub APIs:

• https://developer.github.com/v3/checks/runs/

Prior code that I wrote that works with the check-suites data:

• https://github.com/danwallach/github-classroom-utils/blob/master/github_completion_times.py

Implementation strategy?

• The main RiceChecks doesn't need to change, since it should run as-is on a student machine or in a cloud CI. Grading output in JSON format is already written to the filesystem. That will stick around.
• A new RiceChecks tool would be run from GitHub Actions that would read the grading JSON and would manipulate annotations on the commit.
• Kinda unclear: maybe we want to set up a "check run server" to run the unit tests on every commit and configure RiceChecks to run as a check suite?
  • https://developer.github.com/apps/quickstart-guides/creating-ci-tests-with-the-checks-api