Ability to define the order constraint for ordering groups in 1:N ordering

[novoj]

We're able to sort entities by references that have 1:N cardinality, as described in the documentation. Currently, both non-hierarchical and hierarchical entities are traversed by primary key in ascending order. In some situations, it would be better to traverse them in a more user-friendly way - for example, alphabetically or by some kind or priority attribute set on those referenced entities. This would require extending the capabilities of our query API.