How to extend and collect HAProxy Prometheus Metrics with more labels

Hello:
I am using HAProxy to access other websites, I want to collect the target websites, custom metadata into prometheus metrics, with extending the existing HAProxy Prometheus Metrics. How can I collect the same metrics as HAProxy Prometheus Metrics, including additional target websites, custom metadata as new labels.
extended metrics like:

  • haproxy_frontend_bytes_in_total
  • haproxy_frontend_bytes_out_total
  • haproxy_frontend_request_errors_total
  • haproxy_frontend_http_responses_total
  • haproxy_frontend_connections_total
  • haproxy_backend_bytes_in_total
  • haproxy_backend_bytes_out_total
  • haproxy_backend_http_requests_total
  • haproxy_backend_internal_errors_total