Migrate from Travis CI to GitHub Actions

[gregorbg]

See title. I expect this PR to take some time based on trial-and-error checks, since it is arguably hard to debug CI run without actually running the entire CI.

The Ruby gems at $HOME/.bundle will be automatically cached by the setup-ruby action. The MySQL password of the Ubuntu installation also has to be manually adjusted (the MySQL server that comes with GitHub Actions has root:root instead of Travis' root:[empty]) -> can we change our website Ruby code to use root:root?

Everything else should just be a 1:1 adaptation of the old Travis checks in the new GitHub Actions syntax.

[gregorbg]

Interesting observation: The CI currently fails because the overcommit checks demand that git --config user.name and user.email be set. In the GitHub Actions environment, they are not set by default.

[gregorbg]

Yay, first successful run! Only one non-critical failure about the API to Coveralls not being able to connect via SSL.

Apparently, this happens because the coveralls gem is deprecated and uses TLS 1.1, which was dropped in Ubuntu focal. Migrating to coveralls_reborn as per lemurheavy/coveralls-ruby#163

[gregorbg]

Ready for review!

[jonatanklosko]

Beautiful! 🎉 ❤️

Just some minor comments, please try setting up mysql8 as per one of the comments and we should be ready to go!

[gregorbg]

Had some minor troubles with getting everything uploaded to Coveralls, (potential) fix is already uploaded and running through CI as I write this comment!

[gregorbg]

I have just realised that our previous Coveralls reports (via the Ruby coveralls gem) all cover the spec folder itself. Is this intended/desired?

SimpleCov itself filters the spec folder in its base configuration, implying that this shouldn't be tracked. I can fix our Simplecov to not track /spec but this would result in a significant coverage percentage drop (~96 to ~90). Please advise @jonatanklosko

[jonatanklosko]

SimpleCov itself filters the spec filter in its base configuration, implying that this shouldn't be tracked. I can fix our Simplecov to not track /spec but this would result in a significant coverage percentage drop (~96 to ~90). Please advise @jonatanklosko

Ohh, interesting point! There are different opinions, but I think excluding the test files makes much sense, so I'm up for the new configuration.

I believe we are ready now, or do you want to investigate anything else?

[jonatanklosko]

Ah, feel free to enable the restore-keys as mentioned.

[gregorbg]

Oki, will do! I'll also try out the rails configuration of SimpleCov to see if that changes anything significant

[gregorbg]

Hm, using the rails configuration for SimpleCov really messes things up it seems. I will revert to the status quo including the spec folder and we can worry about handling of coverage in a separate PR to keep concerns clean and my mind sane.

[jonatanklosko]

Awesome work!