* db migration: fix#1844 and add additional assertions
- Migration scripts will now check to see if there are any unconverted
snapshot IDs and fail the migration if there are any. This should
prevent people from getting a corrupt database in the event the root
cause is still unknown.
- Add an ORDER BY clause when doing batch queries in the postgres
migration. LIMIT and OFFSET without ORDER BY are undefined and must
not be relied upon to produce a deterministic ordering (e.g row order).
See https://www.postgresql.org/docs/current/queries-limit.html
* Linting
Co-authored-by: Neil Alexander <neilalexander@users.noreply.github.com>