In particular, check buggy behavior around embedded quoted JSON and Postgres versions, compare https://www.postgresql.org/message-id/D6921B37-BD8E-4664-8D5F-DB3525765DCD%40vllmrt.net This adds version-bounded tests for the handling of quoted JSON, and a pending test that documents the assumption that Postgres >=10 intends to parse quoted JSON as a string (similar to how jsonb works now).