E2E testing when API and front-end are in separate repositories

I have a general question for everyone about end to end testing and how people are achieving full test coverage.

Currently I'm working on a project that has a Laravel API and the front end is Nuxt and in a separate repository.

We currently have a fully test suite for the API which also generates JSON responses for the endpoints from the API tests that are then pushed to another repository which is then pulled into the front-end repo as a git module. This allows us to use these JSON responses in our Cypress integration tests on the front-end.

This is great for most things, but there's a slight whole in our testing, as we can't properly test the authentication sessions, or persisting data between pages.

I would ideally like to be able to run both repo's in our CI pipeline, but also like the separation of the two repositories.

How are others solving this issue, and what are people doing in general to test these harder to simulate scenarios, such as a user complete authentication by confirming an email and then login into an app.