RFC: GitHub status check plugin/hook

[atodorov]

The idea here is to allow Kiwi TCMS to be able to process events from GitHub and report the results back to the database.

For every pull request we have things like:

• Travis CI (multiple jobs) - this can even be its own separate thing
• Code health/static analysis tools (e.g. Scrutinizer)
• Security scanners (e.g. Snyk or PyUp.io)
• anything else really.

See https://help.github.com/articles/about-status-checks/ for starters.

On many projects, even inside of Kiwi TCMS, we merge without everything passing. Things like security issues may not be fixed for a long time. A mechanism to push this information back to Kiwi TCMS would be helpful.

[atodorov]

Now part of kiwitcms/github-app#10