v2.10.0

The db extra drops sqlalchemy-utils and requires a newer alembic. No
public API changes, but check the minimum versions below before upgrading.

Improvements and fixes

• sqlalchemy-utils is no longer a dependency. Creating, dropping and
  checking for a database now use plain SQLAlchemy against the postgres
  maintenance database. If your code imports sqlalchemy_utils, add it to
  your own dependencies
  (database reference,
  #123).
• Dropping a database terminates its open connections with
  DROP DATABASE ... WITH (FORCE), which requires PostgreSQL 13 or later
  (#123).
• The db extra requires alembic >= 1.20.0, which in turn requires
  SQLAlchemy 2
  (#123).