[CI] Only allow reversible migrations

[garyhtou]

For DX, it's nice if all migrations are reversible — I would like that we enforce that with CI.

Does anyone have any thoughts on this? Should we enforce that all (new) migrations are reversible

[polypixeldev]

That would be good

[garyhtou]

It appears you can run bin/rails db:migrate:redo to check whether migrations are reversible.