Function call_actor 

pub fn call_actor<'de, T: Serialize, U: Deserialize<'de>>(
    actor_ref: &str,
    operation: &str,
    msg: &T,
) -> HandlerResult<U>

Performs an actor-to-actor call, with the target actor identified by a reference string. This reference can be an OCI image URL, a 56-character public key (subject), or, if one is defined, a developer-friendly call alias