Implementing project in this blog https://auth0.com/blog/developing-restful-apis-with-python-and-flask/#-span-id--marshmallow-serilization----span--Serializing-and-Deserializing-Objects-with-Marshmallow
http://localhost:5000/expenses
JSON data { "amount": 300.0, "description": "loan payment" }
http://localhost:5000/expenses
JSON data { "amount": 20, "description": "lottery ticket" }