🎨 Bring Python code into compliance with Black and Flake8 (#121)

* Ignore Flake8 unused import error F401

https://flake8.readthedocs.io/en/latest/user/error-codes.html

The apparently unused imports may be needed for SQLAlchemy.

As the code comment says:

make sure all SQL Alchemy models are imported before initializing DB
otherwise, SQL Alchemy might fail to initialize properly relationships

See GitHub 28 and 29

* Ignore Flake8 unused variable error F841

https://flake8.readthedocs.io/en/latest/user/error-codes.html

The apparently unused variables may be needed for tests.

* Bring line length into compliance with Black

Should be 88 characters.

* Format alembic code with Black

{{cookiecutter.project_slug}}/backend/app/app/crud/__init__.py

@@ -1,5 +1,5 @@
-from .crud_user import user
-from .crud_item import item
+from .crud_user import user  # noqa: F401
+from .crud_item import item  # noqa: F401
 
 # For a new basic set of CRUD operations you could just do