added contentful_id to event schema

Author: eino

api/modules/event/model.js

@@ -5,6 +5,10 @@ const Schema = mongoose.Schema;
 const publicFieldsPlugin = require("../../common/plugins/publicFields");
 
 const EventSchema = new Schema({
+  contentful_id: {
+    type: String,
+    required: true
+  },
   name: {
     type: String,
     required: true