message: [lang] Add conversion from OnDeployHandler to Message
  Required by code gen.
diff: @@ -186,6 +186,21 @@ pub struct OnDeployHandler {
  pub block: syn::Block,
  }
  +impl OnDeployHandler {
  + /// Converts this on-deploy handler into its corresponding message.
  + pub fn into_message(self) -> Message {
  + use crate::ident_ext::IdentExt as _;
  + Message {
  + attrs: self.attrs,
  + sig: ast::MethodSig {
  + ident: Ident::from_str("on_deploy"),
  + decl: self.decl,
  + },
  + block: self.block,
  + }
  + }
  +}
  +
  impl From<Message> for OnDeployHandler {
  fn from(msg: Message) -> Self {
  Self {
  