Week5

Including:

- Integration test for resetting password
- Invite Users feature with test
- Refactor with Concerns
- Use Mailgun to send out emails in production
Saving to DB twice may or may not be a concern, and my gut feeling is that it's probably not (maybe 1-5 extra ms?). If performance is a concern, you should build a set of instrumentations to measure and methodically work through bottle necks, and I suggest you do that as a refactor exercise guided step by step with instrumentation/monitoring. During your build up process, don't worry too much about performance.