Allow usage of the store api in app scripts #3145

Effort: middle

Description:

As far as I understood, one should not use the store API in the normal TWIG storefront. But replicating all the logic in app scripts, using TWIG, is quite cumbersome.

Therefore in some hooks, in particular the storefront-{hook} calling the store API should be allowed.

Not really sure if one wants to use the direct function call of the store API route, or rather create a request and dispatch it to the route.

Benefits

Make it easier to create custom endpoints, where logic of store API routes can be combined.

Break strategy

There should be no break, only new functionality.