Function ehsm::get_logged_in_session

pub fn get_logged_in_session(
    ctx: &Ctx, 
    pin: &str, 
    slot_idx: usize, 
    user_type: Option<CK_USER_TYPE>, 
    flags: Option<CK_FLAGS>
) -> Result<CK_SESSION_HANDLE, Error>

A utility function to open a session and log-in