Formatted GraphQL error as returned to the client.
This matches the GraphQL-over-HTTP spec shape. The plugin masks internal errors before formatting.
message: string
Human-readable error message.
optional
locations: Array<{ line: number; column: number; }>
Optional locations in the query document.
optional
path: Array<string | number>
Optional path to the field where the error occurred.
optional
extensions: Record<string, unknown>
Optional extensions for application-specific error codes.