message: [lang] Implement codegen for method impls
  Implements issue
diff: @@ -231,7 +231,28 @@ fn codegen_for_message_impls(tokens: &mut TokenStream, contract: &hir::Contract)
  fn codegen_for_method_impls(tokens: &mut TokenStream, contract: &hir::Contract) {
  let state_name = &contract.name;
  - let methods_impls = quote!{};
  + let methods_impls = {
  + let mut content = quote!{};
  + for method in contract.methods.iter() {
  + for attr in &method.attrs {
  + attr.to_tokens(&mut content)
  + }
  + let fn_decl = &method.sig.decl;
  + fn_decl.fn_tok.to_tokens(&mut content);
  + method.sig.ident.to_tokens(&mut content);
  + let generics = &fn_decl.generics;
  + generics.lt_token.to_tokens(&mut content);
  + generics.params.to_tokens(&mut content);
  + generics.gt_token.to_tokens(&mut content);
  + fn_decl.paren_tok.surround(&mut content, |inner_toks| {
  + fn_decl.inputs.to_tokens(inner_toks);
  + });
  + fn_decl.output.to_tokens(&mut content);
  + generics.where_clause.to_tokens(&mut content);
  + method.block.to_tokens(&mut content);
  + }
  + content
  + };
  tokens.extend(quote! {
  impl #state_name {
  #methods_impls
  