Upgrade to SQLAlchemy 2

[rod-glover]

Why?

• It's been out for 10 months

• This recommendation:

  Release Support: Maintenance Mode

  Please note: the 1.4 series is the current "Maintenance" series. Updates for critical fixes will be made available as needed, but applications which continue to be under active development are advised to begin upgrading to the current series of SQLAlchemy (currently the 2.0 series).

• The code is issuing deprecated feature warnings

• Alembic documentation appears only to be for the latest Alembic version, which in turn is based on the latest SQLAlchemy version

That said, it's going to be quite a bit of work. Read the migration guide thoroughly before committing to this.