GitHub Action that builds and publishes to GitHub Container Registry

[machikoyasuda]

closes #7

part of cal-itp/benefits#127

What this PR does

• Create a new GitHub action called Build and publish Docker image

What this GitHub Action does:

• What: The action builds and publishes the eligibility-server Docker image to the GitHub Container Registry, with specific tags
• When:

1. After pushes to main - the main package is built and updated
2. After a release of main, with a $version-tag-name - the package is built and published with 2 tags: the $version-tag-name, as well as latest

• When: The action filters for pushes to main that touch actual app files (like eligibility_server/app.py or requirements.txt)

How I tested this PR

• I forked this repository, added this GitHub Action workflow file and tried running these scenarios:

1. Merge a PR to main that only edits the README.md: Should not trigger the build and publish workflow
2. Merge a PR to main that edits a relevant app file: Should trigger a build and publish workflow. A package with the tag test should be published: https://github.com/machikoyasuda/eligibility-server/pkgs/container/eligibility-server/8504005?tag=test
3. Create a release: Should trigger a build and publish workflow. A package with the tag with the release name should be published: https://github.com/machikoyasuda/eligibility-server/pkgs/container/eligibility-server

[thekaveman]

Really great start! I requested some changes that will help us read logs and use the action checks in other contexts later if needed. Made a few other suggestions elsewhere.

[machikoyasuda]

Rested this Action in a fork: https://github.com/machikoyasuda/eligibility-server/pull/8

The steps I took:

1. Merge the PR https://github.com/machikoyasuda/eligibility-server/pull/8
2. After which, the main package was updated with this new code
3. After that, I manually created a release called wednesday release and tagged with v0.4

https://github.com/machikoyasuda/eligibility-server/pkgs/container/eligibility-server

[thekaveman]

🚢