Add support for Rails 7.0, 7.1, and 7.2

[mkrfowler]

There are a few changes of interest in this sequence.

* `all_versions` undergoes a rename (to `versions`) from 7.1.
* The `schema_migration` object is accessed via `pool` from 7.2
* Multiple-database support alters the format of `db:version`
* The minimum supported Ruby version is increased in 7.0 and 7.2

As a whole, the existing integration tests remain suitable: there is only the one behavioural change to speak of. As a result, rename the integration test to be less confusing in the presence of non-Rails-6 gemfiles.

[rwojsznis]

Hey there, thanks for this contribution! As I have been away for a while once I will catch up with my day work I will definitely take a look at this :)

Sadly it's been a while since I used this gem and I think we would need to backport more code from Gitlab for proper multi-database support - did you had a chance to run it with a real-life project after introducing suggested changes? 🤔

ref: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/64884

[mkrfowler]

Hey there, thanks for this contribution! As I have been away for a while once I will catch up with my day work I will definitely take a look at this :)

Thanks, I've certainly been at very low availability myself!

Sadly it's been a while since I used this gem and I think we would need to backport more code from Gitlab for proper multi-database support - did you had a chance to run it with a real-life project after introducing suggested changes? 🤔

ref: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/64884

I agree that full-fledged multi-database support will want some of this work to be ported over – for instance, the implementation of #schema_directory from that changeset. My own projects don't make use of the parts of that functionality that actually exercise migrations – I suspect with little evidence that this is relatively rare. I'd probably bias to that being a separate set of changes myself.

We've been using the current version of this gem under Rails 7.0 for a while now with no issues. These changes are motivated by a real-world 7.1 update. I see reasonable behaviour both with that codebase and (more tentatively) the same application updated to Rails 7.2.

[rwojsznis]

thanks for the context & feedback!

I will review and release new version of this gem with a note that 7.x support is a little bit limited (a.k.a. no multi-database support)

It would be great to port all those new changes from Gitlab eventually tho 😩