Saves the token to your local keychain under a service called "appeears".
user used to sign up for the AppEEARS data service (this is not the email address, but the true user name!)
used to sign up for AppEEARS
It invisibly returns the user.
In systems without keychain management set the option keyring_backend to `file` (i.e. options(keyring_backend = "file")) in order to write the keychain entry to an encrypted file. This mostly pertains to headless Linux systems. The keychain files can be found in ~/.config/r-keyring.