Custom webhook - unable to send subject & message details

Hi,

I am using a Custom Webhook configuration. Where in my inbound API supports the “summary” and “details” attributes in place of “subject_template” and “message_template” in custom webhook integration.

Am able to send the notifications to my webhook endpoint but the Subject & Message details are not showing up. Below is my monitor & destination API’s. Kindly, let me know if am missing something.

Monitor:

POST _plugins/_alerting/monitors
{
  "type": "monitor",
  "name": "test-goalert-monitor",
  "monitor_type": "query_level_monitor",
  "enabled": true,
  "schedule": {
    "period": {
      "interval": 1,
      "unit": "MINUTES"
    }
  },
  "inputs": [{
    "search": {
      "indices": ["<index-name>"],
      "query": {
        "size": 0,
        "aggregations": {},
        "query": {
          "bool": {
            "filter": {
              "range": {
                "@timestamp": {
                  "gte": "||-1h",
                  "lte": "",
                  "format": "epoch_millis"
                }
              }
            }
          }
        }
      }
    }
  }],
  "triggers": [{
    "name": "test-trigger",
    "severity": "1",
    "condition": {
      "script": {
        "source": "ctx.results[0].hits.total.value > 0",
        "lang": "painless"
      }
    },
    "actions": [{
      "name": "test-action",
      "destination_id": "<dest-id>",
      "message_template": {
        "source": "This is my testing message body."
      },
      "subject_template": {
        "source": "TESTING"
      }
    }]
  }]
}

Destination:

POST _opendistro/_alerting/destinations
{
  "type": "custom_webhook",
  "name": "destination-name",
  "custom_webhook": {
    "path": "api/v2/generic/incoming",
    "header_params": {
      "enabled": true,
      "Content-Type": "application/json"
    },
    "scheme": "HTTP",
    "port": <port-ip>,
    "query_params": {
      "token": "<token>",
      "message_template": "details",
      "subject_template" : "summary"
    },
    "host": "<host>"
  }
}