Rails 7 Support

[tpendragon]

This PR is an adjustment of #892 to include general Rails 7 support.

Original message from @cgalarza :

I am working on adding Valkyrie to a fresh Rails 7/Ruby 2.7 application, but I am having trouble because Rails 7 deprecated the connection_config method available in ActiveRecord in favor of connection_db_config. In this PR, I attempt to choose the appropriate method based on what’s available.

For the specs, I wasn’t sure how best to test the ID generation. Should I specifically check that the host and database are set to the correct values instead of just checking that they are non-null values?

The pipeline fails because of coverage. With this solution it would not be possible to get 100% coverage for the connection_configuration method. What should I do?

I am pretty sure I have an individual CLA on file, is there a way to check? I am asking now if UPenn has a corporate one on file and if we just need to add my name to it.

Thanks for taking a look at this! Please let me know if there's anything I should change.

[tpendragon]

@cgalarza Here's the PR. I added some mocking business to get around the coverage issue, can you take a look and see how it feels?

[cgalarza]

@tpendragon Using mocking to get around the coverage issue is really clever! PR looks good to me. I also just confirmed that I have an iCLA on file and that UPenn has a cCLA on file.