Enable Subitem Reordering via GraphQL

Description

Our team manages a highly dynamic board where subitems often need to be automatically reordered based on calculated parameters or workflow logic.

Currently, GraphQL supports reordering for parent items — which is extremely useful — but this functionality isn’t yet available for subitems. Extending this capability to subitems would allow developers to maintain consistency between automation logic and board structure, especially when working with nested data relationships.

What are you trying to achieve

Use case example:
We have automations that update subitem properties (like priority or status) based on real-time data. Being able to reorder those subitems through GraphQL would let us dynamically organize them (e.g., by urgency, completion stage, or calculated metrics) without manual intervention.