Constructing a new AtSign should only require &str

[Zambrella]

Is your feature request related to a problem? Please describe.

Calling read_data(...) in a loop requires cloning and constructing new AtSign object each time.

loop {
        let at_contact = AtSign::new(contact.clone());
        at_client
            .read_data(at_contact, "attalk")
            .expect("Failed to read data");
        thread::sleep(time::Duration::from_secs(4));
    }

Describe the solution you'd like

There is no reason for the AtSign::new() associated function to require String when &str will do. The same is true of the read_data(...) method.

Describe alternatives you've considered

No response

Additional context

No response