Summary

FgaApiAuthenticationError currently extends FgaError instead of FgaApiError.

Impact

Authentication failures are excluded from API-error polymorphism:

• instanceof FgaApiError checks fail for authentication errors
• shared API error handling paths can miss auth failures
• FgaApiAuthenticationError duplicates metadata fields instead of inheriting the common API error shape

Expected

FgaApiAuthenticationError should inherit from FgaApiError like other API-derived errors.

Proposed Fix

Change inheritance to:

export class FgaApiAuthenticationError extends FgaApiError

and keep auth-specific fields and message behavior.