[Parse] Investigate sessionToken

[yinanfang]

https://parseplatform.github.io/docs/js/guide/#setting-the-current-user

Parse.User.become("session-token-here").then(function (user) {
  // The current user is now set to user.
}, function (error) {
  // The token could not be validated.
});

Retrieve session token: https://www.parse.com/questions/accessing-current-users-sessiontoken-from-cloud-code

Safe to store sessionToken in JWT since the data extract only happens on server and server Parse SDK require APP_ID, which is like a password https://github.com/ParsePlatform/parse-server/wiki/Parse-Server-Guide#user-content-keys