Migrate CI / CD to GitHub Actions

[defagos]

As a Pillarbox developer I want a reliable CI orchestrated using GitHub Actions.

Acceptance criteria

• All existing CI tasks can be run through GitHub Actions on self-hosted hardware.
• Tasks perform in reasonable time.

Tasks

• Update scripts to be run with pkgx.
• Create dedicated workflows.
• Replace private configuration repository with GitHub secrets (p12 certificate and associated password, p8, other info).
• Make repository structure simpler (e.g. no more need for symlinks to .env).
• Create workflow for nightly / release demo builds.
• Ensure steps fail correctly (e.g. if one test fails the test step must fail). See this example.
• Update repository configuration.
• Integrate with GitHub deployments.
• Only keep make targets that can be run locally.
• Update developer documentation (in particular the required tool list after migration).
• Optimize test suite (identify tests that take too long or reach the timeout, tweak timeouts, etc.).
• Document CI setup, replacing the old Team City documentation (e.g. secrets and envvars to setup).
• Archive or delete existing configurations on Team City.
• Archive private configuration repository (update Fastfile accordingly).
• Archive GitHub Actions PoC repositories (keep them for future reference if needed).
• Inform other teams we have left the TeamCity CI.

[defagos]

For the moment we decided not to fix any macOS / tool version and to always use the latest versions available. Best practices would probably recommend to fix versions but we'll see if this is really an issue and adjust accordingly (it never really was with our old CI pipeline).

[defagos]

We discussed about updating our scripts to ZSH (now the default on macOS) but this will be delayed until shellcheck supports it.