Check validity of authentication token

[NicolasMahe]

The function setAuthenticationToken should first check if the token is valid (not expired) and then set it.

We already have the logic implemented in the currentAddress:

liteflow-js/packages/hooks/src/context.tsx

Lines 52 to 58 in 125f909

	const [authenticationToken, setAuthenticationToken] = useState<string>()
	const client = useMemo(() => new GraphQLClient(endpoint), [endpoint])
	const sdk = useMemo(() => getSdk(client), [client])
	const currentAddress = useMemo(() => {
	if (!authenticationToken) return null
	const res = decode<JwtPayload & { address: string }>(authenticationToken)
	if (res.exp && res.exp < Math.ceil(Date.now() / 1000)) return null

We could add a new public function isAuthenticationTokenValid that could be use in different places and also by the apps

Existing logic in https://github.com/liteflow-labs/admin/blob/main/session.ts