Aren't we attacking this on the wrong level? We are here attempting to prevent a SCRAM-SHA-256-PLUS -> SCRAM-SHA-256 downgrade, but we are not preventing a SCRAM-SHA-256-PLUS -> anything-else downgrade.
-- Peter Eisentraut http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services