[Rspec] Efficiently Speed Rspec test

參考第一篇文章

author has deleted
https://medium.com/the-code-review/5-rspec-tips-to-speed-up-testing-ruby-on-rails-projects-db8759a20869

Conclusion
前面 1 ~ 4 點，學習一些技巧和寫法，但是效能提升没特別提到
但文章的第 5 點 Efficiently load data records 得到几个方向

1. Use let, rather than let!
2. One is to use before_all instead of before_each in a test file
3. Another is to have a global variables file, which loads an instance of each record before all tests start
4. Another approach is to user FactoryBot’s build_stubbed method