An error occurred while installing mysql2 (0.5.2), and Bundler cannot continue. Make sure that `gem install mysql2 -v '0.5.2' --source 'https://rubygems.org/'` succeeds before bundling.と出てきたときの対処法② - Qiita
Monorepo , React +Rails api, PG Issue on Deployment: Can't find the 'libpq-fe.h header - Support - Netlify Support Forums