Rails dependency likely not needed

[langalex]

It would likely be enough to depend on railties instead of rails. The benefit would be that apps that don't use all of Rails' features (e.g. actioncable, activestorage) can be shipped without these extra gems.

[ndbroadbent]

Oh that would be awesome! I would be interested in seeing how this works in practice. Would you be interested in helping out with a PR and some extra test cases? Perhaps we could have another e2e test suite that does a barebones railties setup instead of the full test app.