Export: add _format field

models/export.js

@@ -42,6 +42,7 @@ class Exporter {
     // we do not want to retrieve boardId in related elements
     const noBoardId = {fields: {boardId: 0}};
     const result = Boards.findOne(this._boardId, {fields: {stars: 0}});
+    result._format = 'wekan-board-1.0.0';
     result.lists = Lists.find(byBoard, noBoardId).fetch();
     result.cards = Cards.find(byBoard, noBoardId).fetch();
     result.comments = CardComments.find(byBoard, noBoardId).fetch();