Refactor flask models to use blueprints

[masonlr]

Goal

Blueprints allow for more separation between python code fragments and the API endpoints that they are wired to. If we decide later that a certain python fragment should be moved from, say, users to accounting, blueprints will make this easier.

Acceptance criteria

• [ ] Middleware refactored to implement flask blueprints

Out of scope

Implementation notes

• See, for implementation example, https://github.com/realpython/flask-jwt-auth/blob/master/project/server/auth/views.py

[masonlr]

The blueprint and testing implementation of https://github.com/realpython/flask-jwt-auth looks solid. I would really like to deploy this to Azure, but cannot work out how to. I cannot determine the correct setting for WSGI_ALT_VIRTUALENV_HANDLER in the web.config file.