Store credentials to avoid errors (given consent)

[kmchmk]

Currently we only store the refresh token in local storage every 2 minutes. But I've noticed that sometimes some login errors occurs and then the existing refresh token in memory becomes invalidated. Sometimes this can be solved by restarting the program but sometimes it doesn't and when restarted, it requests login credentials again. This issue can be solved easily if we have credentials stored.

So given the owners permission, we can store the credentials to be used when needed.