Broken access control in AshGraphql subscription batcher applies authorization suppression to only the first notification

Incorrect Authorization vulnerability in ash-project ash_graphql delivers GraphQL subscription payloads for records a subscriber is not authorized to see.

In AshGraphql.Subscription.Batcher, do_send/5 resolves the first notification of a batch and filters it with should_send?/1, which drops results whose errors are coded forbidden or not_found or carry no code, precisely so that unauthorized results are not disclosed. The remaining notifications in the batch are read from the process dictionary, re-run through the pipeline, and appended to the outgoing results without that filter. They reach pubsub.publish_subscription/2, and the not is_nil(record) guard drops only nil records, not error-carrying results. Any two qualifying notifications arriving within the default one-second batch interval suffice, and batching is the default path. The fix applies should_send?/1 to the whole batch.

This issue affects ash_graphql: from 1.4.0 before 1.11.0.

The application exposes ash_graphql subscriptions with Ash authorization enabled, and two or more notifications are batched together within the batch interval (the default path).