Sort over Aggregations buckets by text field over already sorted result

Elastic Stack Elasticsearch
1

I am currently facing an issue with sorting aggregation results on a text field in Elasticsearch. this is my query

{
  "size": 0,
  "query": {
    "bool": {
      "must": [
        {
          "query_string": {
            "fields": [
              "username",
              "fullname"
            ],
            "query": "\"ayan\""
          }
        }
      ]
    }
  },
  "aggs": {
    "total_count": {
      "cardinality": {
        "field": "userid"
      }
    },
    "group_by_userId": {
      "terms": {
        "field": "userid",
        "size": 10,
        "include": {
          "partition": 0,
          "num_partitions": 2
        }
      },
      "aggs": {
        "latest_login": {
          "top_hits": {
            "_source": {
              "includes": [
                "username",
                "userid",
                "logintime",
              ]
            },
            "sort": [
              {
                "logintime": {
                  "order": "desc"
                }
              }
            ],
            "size": 1
          }
        }
      }
    }
  }
}

now i need to sort the group_by_userId bucket with username field or createdtimefield which depends on situation. I'm able to sort it with createdtimefield because it was a datetime field. by adding bucket_sort with max but I could not found a way to do it with the username.