Unclear how to relate reinforcing to the element (e.g. slab)

Brought up [here](https://forums.buildingsmart.org/t/implementation-of-ifc-preprocessor/3198)

Confirmed that the docs make no mention of how reinforcement gets assigned to slabs / columns / beams / etc. One method I would assume is IfcRelAggregates but it seems very annoying to have to turn it all into an aggregation just for this association. Kinda like how in every single mode you see walls, slabs, beams .... _except_ in steel models like from Tekla where now _everything_ is grouped into an IfcElementAssembly even though in 99% of the cases the assemblies only contain one object: the Beam.

Sorry, that was just a rant - it basically doubles the element count to deal with in a project, and with steel you're already running into 100k objects easily. Not sure if relevant to this discussion.