TIL, 2018-09-22, Don't Use the Word 'User'

[Reference](Never use the word “User” in your code)
- Airline system “users”: Are different based on the context (traveler, purchaser, travel agent, check-in agents).
- Unix “users”: Humans who log in, system services, admin accounts who are SSHing into the server, and root.
- SaaS: Almost always, there is a person who is paying for the service, and one or more people from that organization who actually use the service.
- If you combine them from the start, then you can’t model teams, payment for multiple people at once, and now you need to change it later.
Rails locking:
- Product.transaction do ... end is the same as Product.find(1).transaction do ... end.