Function add_account 

pub(crate) fn add_account(
    qt: &CxxQtThread<Sioul>,
    shared: &Arc<Shared>,
    address: String,
    url: String,
    login: String,
    password: String,
)

Adds a contacts-and-calendars account: finds where they are, tests the password, keeps it in the keyring, and starts syncing. On a thread.