rails new my_app_name --database=postgresql

https://medium.com/@frouster/ruby-on-rails-postgresql-f1b037924bdf
https://www.digitalocean.com/community/tutorials/how-to-set-up-ruby-on-rails-with-postgres
https://www.ionos.com/digitalguide/server/know-how/use-postgresql-with-ruby-on-rails-on-ubuntu/
#Install Rails
gem install rails
#Install Postgress
gem install pg
#Setting Up Postgres
su - postgres
psql
create role myapp with createdb login password 'password1';
#Creating Your Rails App
rails new myapp --database=postgresql
#More
rails db:create db:migrate