For users that only want to work with templates we need some powerful base controllers out of the box regarding content loading in different views and ways (embed and regular) but also content traversal, aka search filtering.

In legacy this was accomplished with fetch functions, and gg even had a proposal to simplify that further so this feature would be about finding a way to allow such use cases while still playing on the strengths of Symfony*.

This can be implemented on top of #EZP-22344, but does not have to, it just makes sense to sync the convention used on this and #EZP-22344 in regards to naming of the filters.

* An example of that would be something like this which maps to content and location filtering respectively:

{{ render( controller( 'MyBundle:content:list', { 'type': 'image', 'related-to':  33, 'limit' : 10 } ) ) }}
{{ render( controller( 'MyBundle:location:tree', { 'type': ['image', 'file'], 'parent':  44, 'depth': 3, 'limit' : 10, 'offset': 10 } ) ) }}

However additional synthetic sugar can be added on top of that in form of a twig extension to simplify it further.