I see the project has some issues related to github action.

1. Turn on Brakeman (Currently, it is configured to run only for master branch, which means it has never been activated before)
2. Turn on "Tests - PostgreSQL" on pushes (or only on push to main branch)
3. Discuss "Tests - MySQL". Now, they manually disabled so i think we should remove or restore unusual action to avoid future confusions.
4. Change badges on README.md to show statuses from main branch (Right now, it's confusing because all actions appear as failed.)

I'd like to work on fixing these issues.