CI: Test against rails 7.0

[meganemura]

Why?

This PR aims to update the CI configuration to support testing for Rails 7.0, which is an important update for the project. Ensuring compatibility with Rails 7.0 will make the project more robust and up-to-date, as well as maintain support for the latest features and improvements.

What?

The changes made in this PR involve updating the CI configuration to run tests targeting Rails 7.0. This will help ensure that the project remains compatible with the latest version of Rails and that any potential issues or conflicts are detected and addressed promptly.

Caveats

In this pull request, the CI configuration has been updated to run tests for Rails 7.0. However, it is unverified whether this is sufficient for full compatibility with Rails 7.0.

Testing Notes

• Test that the CI pipeline runs successfully with Rails 7.0
• Test that all existing tests pass with Rails 7.0

Alternatives Considered

N/A

Further Reading

• https://guides.rubyonrails.org/upgrading_ruby_on_rails.html
• https://rubyonrails.org/2023/3/13/Rails-7-0-4-3-and-6-1-7-3-have-been-released

Merge Instructions

Please DO NOT squash my commits when merging.

[meganemura]

@katsuyasu-murata @valerauko

When you have a moment, could you please take a look at this PR?

[valerauko]

We're tweaking the CI now so that tests can run from forked PRs

[valerauko]

@meganemura thanks for your contribution!