constants
VERSION_DATE_STRING = '%Y-%m-%dT%H:%M:%S'
module-attribute
sqlalchemy defaults to a type of Optional[str] even when a column is set to be not nullable.
This is per their documentation. One option is to add type:ignore for python objects that
should not be nulls and are mapped to sqlalchemy ORM objects. Alternately, as is here,
we can add a placeholder. This will be used like obj.property = ormobject.property or placeholder.
This should separate out the ORM objects and their policy of setting all columns to be
Optional vs app objects that should reflect the app's expectation of not allowing nulls.
The app object's property does not get set to None and the ORM object doesn't need to worry
about knowing what the app is doing.