logout

Signs the user out: clears the credentials this device holds and revokes the token with LINE.

Idempotent, and safe to call when nobody is signed in — with no session to revoke it simply reports LineLogoutResult.Success.

A LineLogoutResult.Failure means LINE was not reached, so the token was not revoked server-side. It expires on its own, and the SDK has already dropped its local copy either way, so the user is signed out of your app regardless.

On web the revocation half does not exist: LIFF clears this browser's tokens and offers no client-side revoke, so the grant itself survives until it expires or the user removes it from their LINE account settings.