Add better types to models.py

[smcmurtry]

Summary | Résumé

Add better types to models.py.

How this works:

• the db object in models.py is an instance of the RoutingSQLAlchemy class defined here: https://github.com/cds-snc/notification-api/blob/main/app/dbsetup.py#L70
• RoutingSQLAlchemy has flask_sqlalchemy.SQLAlchemy as a base class
• flask_sqlalchemy.SQLAlchemy has the following in its docstring:

This class also provides access to all the SQLAlchemy functions and classes from the sqlalchemy and sqlalchemy.orm modules

• most of the things that are missing types in models.py can be found in these two paths, for instance db.Column is of type sqlalchemy.Column, db.Boolean is of type sqlalchemy.Boolean, db.relationship is of type sqlalchemy.orm.relationship
• so I just imported all the classes from these two paths into a new file, app/db_type.py, and assigned the db object to be that type
• that populates most of the types in models.py:

Before:

After:

Test instructions | Instructions pour tester la modification

Tests should pass in CI, check out and try the new type hints locally!

[jimleroyer]

Let's please document the purpose of this file with a docstring, explaining why this is necessary.

[jimleroyer]

And a comment to explain why we need to cast it to the module's type. 👍