oauth-jsclient: isAccessTokenValid() gives false positive result

The isAccessTokenValid() function always returns true if token has expires_in greater then 60.

Tried to dig deeper and found that internal _checkExpiry() function makes use of createdAt property. The internal setToken() function sets now if its missing in provided token this.createdAt = tokenData.createdAt || Date.now()

Note, createToken() does not provide createdAt in the response, so SDK user cannot provide that in token.

In other words, if createdAtis missing in provided token, then system sets Date.now() and uses that in expiry computation (plus 60 sec latency)., thus gives false positive result.