[Bug] Disallow sorting by child fields that are arrays

Bug report

In a subgraph schema like

type Parent {
  id: ID!
  children: [Child!]!
}

we allow a query like parents(orderBy: children__id) { .. } but that ordering doesn't make much sense. When a parent has multiple children, it's not clear which child's id we will use for the ordering. We should simply not support that.

Some information to help us out

• Tick this box if this bug is caused by a regression found in the latest release.
• Tick this box if this bug is specific to the hosted service.
• I have searched the issue tracker to make sure this issue is not a duplicate.

OS information

None

Nell'issue non sono indicati file, test o punto di ingresso. Inizia tracciando come vengono convalidati i campi GraphQL orderBy per le relazioni annidate, quindi riproduci il caso di schema Parent/children; il lavoro è completato quando l'ordinamento per un campo di tipo array di un elemento figlio viene rifiutato, mentre le relazioni scalari supportate rimangono valide.