Kiwitcms-github-app

- Don't crash on 404 from GitHub. Fixes KIWI-TCMS-EA
- Workaround upstream https://github.com/PyGithub/PyGithub/pull/2079. Fixes KIWI-TCMS-HD

- Update for newer PyGithub

- Adjusted to work with Django 3.1 and Kiwi TCMS > 8.6
- Replace deprecated ``url()`` with ``re_path()``
- Migrate the ``payload`` field to newer ``models.JSONField`` type
- Setting ``PUBLIC_VIEWS`` is removed in Kiwi TCMS so remove the
automatic adjustment
- Make error messages for missing AppInst more clear
- Remove redundant if condition in Resync()
- Update translation strings
- Update documentation around GitHub permission requirements for
1-click bug report

- Add GitHub issue-tracker integration which authenticates as the installed app. Fixes Issue 25
- Configure BugSystem for new repos. Fixes Issue 15
- Create Product & BugSystem records when installation_repositores change. Fixes Issue 21
- Trigger resync from GitHub via menu. Fixes Issue 19
- Trigger resync from GitHub after AppInstallation is configured. Fixes Issue 20
- Database: Add AppInstallation.settings_url field
- Link to the correct URL for GitHub settings. Fixes Issue 33
- Require user to be logged in for ApplicationEdit. Fixes Issue 36
- Update translation strings
- Add more tests