authSignInErrorMessage
fun Throwable.authSignInErrorMessage(providerName: String, genericFailureMessage: String = "Sign in failed. Please try again."): String
Maps a sign-in failure to a short, user-facing message.
Detects the common "package certificate hash mismatch" failure mode (Google/Firebase Auth SHA-1 fingerprint misconfiguration) and surfaces a distinct, actionable message for it instead of a raw, developer-facing exception string.