[Bug] Disallow sorting by child fields that are arrays

[lutter]

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.
• [X] I have searched the issue tracker to make sure this issue is not a duplicate.

OS information

None

[github-actions[bot]]

Looks like this issue has been open for 6 months with no activity. Is it still relevant? If not, please remember to close it.