[needs triage] Extending Add To Cart

[ymirek]

Is your feature request related to a problem? Please describe.
It's often required to extend add to cart with additional parameters (like transport unit, delivery date or others).
We would like to extend this method but requireLoadedCart() is private:

spartacus/projects/core/src/cart/facade/active-cart.service.ts

Line 383 in 4179772

this.requireLoadedCart()

Describe the solution you'd like
Make requireLoadedCart() protected or public

Describe alternatives you've considered
No other choice than duplicating entire ActiveCartService.

Additional context

[Platonn]

It's already made public in Spartacus 3.1.0-next.0 (PR #5347).