fix: make groupBy as an array of strings of column names

Signed-off-by: Muhammad Aaqil <[email protected]>

Author: aaqilniz

lib/sql.js

@@ -1266,8 +1266,7 @@ SQLConnector.prototype.buildFields = function(model, data, excludeIds) {
  * @returns a part of query for group by as a string
  */
 SQLConnector.prototype.buildGroupBy = function(groupBy) {
-  const groupByColumns = Object.keys(groupBy);
-  return 'GROUP BY ' + groupByColumns.join(',');
+  return 'GROUP BY ' + groupBy.join(',');
 };
 
 /**