✨: LIB-538 Refactor + add Dafalgan support

[Coniface]

Notes

• I supposed this was a single task handed with ticket number LIB-538 but I think it should be split in several sub-tickets and therefore successive pull requests. I did only one pull request to ease your review process and not spread it across multiple PRs.
• I created a wiki.md file in the project to keep the documentation in the same place than my project. But I would recommend using Github's wiki feature if possible. I didn't use it here to avoid creating a second project.
• I did not spend more time on Typescript configuration but it should be tuned for using node in production (and not ts-node!)
• I used a JS getter/setter on Drug.benefit because the exercises specifies that the public API should not be changed and I wanted to add the check for benefit value ($0 ≤ benefit ≤ 50$). I would prefer using a setBenefit method as it is more explicit to me but it was not possible here. I'd love to hear what you think about that setter.

Process

• I started with writing a quick documentation that regroups all the important information in a single place. I added some visuals to it (one diagram and tables) to make things clear before starting developments.
• I then refactored the project's structure.
• I replaced babel with typescript straight away so I could use it for my tests (although the tests should have been the second thing to do after documentation to ensure no regressions).
• I added more tests to the existing test file. Although it is not the target architecture, it is important to avoid regressions during developments.
• I refactored the Drug class as to me, the Drug (model) must be aware of its own logic, not the Pharmacy (controller).
• BREAKING CHANGE To use my newly implemented classes, I had to forbid the creation of a Drug based on a name. If the Drug class is not abstract, it is possible to create a new Drug('Fervex', 30, 20) that will behave as a Drug instance despite the name 'Fervex' passed to the constructor. The developper should use the Fervex class so its instance has the overridden method of updateValues() corresponding to Fervex's logic.
• I completed my quick documentation with the new Dafalgan rules.
• I implemented the Dafalgan support.

I did not add the Dafalgan to the index.ts as it is not required by the instructions and it would modify the output.txt.

Time Management

In total, I spent around 4 hours on the tests:

• ~1h30 reading the test, analyzing the legacy code and writing a first documentation.
• ~1h setting up the environment and project with proper tooling (could be greatly improved, lost some time here)
• ~1h30 refactoring the drugs with a clean API, writing tests for each of them
• ~10m adding the Dafalgan (easy and enjoyable once everything is neat 🚀)

Many Thanks! 🎉

If you're reading this, it means you took time to review my PR properly so... Thanks a lot!
I never had a refactoring project as a technical test, I think it's a great idea and this one was fun to tackle.

I would be really glad to hear your feedbacks regarding my work, whether it's a full review here or a call.
I would also love to know how you would have done it, if you have any advice regarding anything (code, patterns, tests, tools, git practices...), I am always eager to further improve.