Ruby test and lint github action workflow

[abachman]

This PR introduces a workflow for running the Rails test suite and Ruby Standard linter on pull requests for the project.

This workflow works as currently written, but fails checks because we have test failures and linter violations.

Once those issues are fixed, we can add it as a branch protection in the project settings.

[jonny5]

One small comment, LGTM if that is intended 👍

[jonny5]

is this intended? (not too familiar with myself)

[h-m-m]

I think one port is the port inside the container and the other is outside the container (or the other way around)

[abachman]

Yes! This lets the postgres docker image be useable from your host machine.

So if you're comfortable with docker, you could run docker compose up -d db from this project directory and have Postgres without having to install it on your OS directly.

[abachman]

in docker configuration--ports and volumes in particular--the colon-separated thing:thing refers to outside:inside or host:image.

In this case, 5432:5432 read left to right says, "expose on port 5432 on my host machine the port 5432 from inside the docker container".

When we use a single value like 5432, it means "the docker container I'm describing should expose port 5432 to other containers on the same network." "The same network" here means the other services named in docker-compose.yml.