Items to do:

• check for deprecation messages in current production logs
• upgrade Rails and dependent gems
• go through upgrade guide points 1 and 2
• go through notable changes in release notes
• remove workarounds and monkey patches in code pointed to by `rg -i "rails \d"`
• regenerate database schema as Rails 6.0 updated format
• make sure oracle-enhanced works
• Set load_defaults to 6.1 at application.rb

Note about Ruby/Rails compat matrix: https://www.fastruby.io/blog/ruby/rails/versions/compatibility-table.html