Function action_message 

pub fn action_message(
    surface_id: &str,
    component_id: &str,
    name: &str,
    context: Value,
    payload: Option<Value>,
    timestamp: &str,
) -> Value

A client action message (A2UI v0.9 action). context null = {}; payload only when it has keys (JS Object.keys(payload).length).