Cascade user deletion in related rows of tables of this module

[fenekku]

Is your feature request related to a problem? Please describe.

Deleting a user should cascade to the related rows in the tables defined by this module.

Currently, attempting to delete a user marks the foreignkey as null but since nullable=False, an integrity error is raised and the transaction is aborted.

Describe the solution you'd like

Add a backref cascade in appropriate places so that related rows gets deleted nicely. Example:

from sqlalchemy.orm import backref

class RemoteAccount(db.Model, Timestamp):
    # ...
    user = db.relationship(User, backref=backref('remote_accounts', cascade="all,delete"))
    """SQLAlchemy relationship to user."""

Describe alternatives you've considered

I have to delete from the bottom up i.e. figure out all models keying into User and delete those... ugh