introduced now_helper for multidb capabilities

backend/models/now_helper.js

@@ -0,0 +1,13 @@
+const db     = require('../db');
+const config = require('config');
+const Model  = require('objection').Model;
+
+Model.knex(db);
+
+module.exports = function () {
+	if (config.database.knex && config.database.knex.client === 'sqlite3') {
+		return Model.raw('date(\'now\')');
+	} else {
+		return Model.raw('NOW()');
+	}
+};