message: [model] Support optional trailing comma in state! macro
diff: @@ -42,6 +42,24 @@ macro_rules! state {
  $field_name:ident : $field_ty:ty
  ),*
  }
  + ) => {
  + $crate::state! {
  + $vis struct $state_name {
  + $(
  + $( #[$field_meta] )*
  + $field_name : $field_ty ,
  + )*
  + }
  + }
  + };
  + (
  + $( #[$state_meta:meta] )*
  + $vis:vis struct $state_name:ident {
  + $(
  + $( #[$field_meta:meta] )*
  + $field_name:ident : $field_ty:ty ,
  + )*
  + }
  ) => {
  $( #[$state_meta] )*
  $vis struct $state_name {
  