message: Introduce SetMetafield
diff: @@ -127,7 +127,11 @@ interface AddShippingLineChange {
  phone?: string;
  }
  -type Changes = (AddVariantChange | AddShippingLineChange)[];
  +interface SetMetafield extends Metafield {
  + type: 'set_metafield';
  +}
  +
  +type Changes = (AddVariantChange | AddShippingLineChange | SetMetafield)[];
  interface Changeset {
  changes: Changes;
  