Refresh the token only when it is still valid but within
TOKEN_REFRESH_WINDOW_MS of expiring. Safe to call on every app
launch: a no-op when there is no token, the expiry is unknown, it is not yet
due, or it has already lapsed (an expired token can't be refreshed).
Refresh the token only when it is still valid but within TOKEN_REFRESH_WINDOW_MS of expiring. Safe to call on every app launch: a no-op when there is no token, the expiry is unknown, it is not yet due, or it has already lapsed (an expired token can't be refreshed).