Add support for Rails 7

[tagliala]

Close #749

[tagliala]

For the moment, this is locally executed with a fixture that I've committed in #751:

$ FIXTURE={rails7} bundle exec rake test:clean test:setup test:fixtures
*** Running tests for rails7... ***

# Running:



Finished in 0.000606s, 0.0000 runs/s, 0.0000 assertions/s.
0 runs, 0 assertions, 0 failures, 0 errors, 0 skips
...................................................
51 passes, 0 failures, 0 errors in 0.308690 seconds