Code updated to Flask v2

• Updated flask version to 2v2
• Updated pymongo to v4
• Added python-dotenv to be able to read the .flaskenv file
• Updated README
• Added .flaskenv file to tell Flask where to app lives
• No longer necessary to set PYTHONPATH manually when running app with flask run

Current course code

This release contains the code exactly as shown in the course, which has a small issue:

In order to run the code you need to manually set the PYTHONPATH to be the repo folder. That's because when you run the app using python src/app.py, Python won't be able to import from the src folder, even though all the imports in the code are in the style of from src.models import ....

So if you want to see the code exactly as is in the course, look at this release. If you want a version of the code with an update that makes it easier to run, please check out the v2 release and the README in the master branch.