Macro msg 

macro_rules! msg {
    ($payload:expr $(, $key:expr => $val:expr)* $(,)?) => { ... };
    ($payload:expr, $kind:expr $(,)?) => { ... };
}

A macro to create a CanonicalMessage easily.

Examples:

use mq_bridge::msg;

let m1 = msg!("hello");
let m2 = msg!("hello", "greeting");
let m3 = msg!("hello", "kind" => "greeting");

#[derive(serde::Serialize, Clone)]
struct MyData { val: i32 }
let m4 = msg!(MyData { val: 42 }, "my_type");