feat: add support for multiple databases with ActiveRecord

[n-studio]

fixes #10

https://guides.rubyonrails.org/active_record_multiple_databases.html

[benlangfeld]

Is there a way we can test this?

Please also include a changelog entry :)

[n-studio]

Is there a way we can test this?

Please also include a changelog entry :)

I updated the changelog entry. I have no idea how to test it, but if you have an idea I can implement it.

[benlangfeld]

@aried3r How much do you care about test coverage for this, considering the difficulty in setting up multiple databases in CI?

[aried3r]

I haven't yet needed to test multi-db Rails setups on CI myself, so I have to ask naively, shouldn't it be – at least for PostgreSQL – "just" another call do createdb?

I don't want to test Rails itself, but if there was even a single test that confirms that two DBs are being used, I'd appreciate it.

Could we also add a little bit of documentation to the README?

[nicdal]

Any plans to merge this to master?