update webhook docs

Author: pijiang3

en/on-call/integration/webhooks/incident-webhook.mdx

@@ -1,5 +1,3 @@
-<Tip>**Plan requirement**: This feature requires an On-call Standard or higher subscription. [Learn more](https://flashcat.cloud/flashduty/price/)</Tip>
-
 Configure incident Webhook. When specific operations occur on incidents (such as trigger or close), the system makes an HTTP callback to your configured address. The callback content includes the incident's latest key information, allowing integration with your custom tools.
 
 <span id="EventTypes"></span>
@@ -14,6 +12,7 @@ The following event types are currently supported; more may be added in the futu
 | :----------: | :--------------- |
 | i_new | Create incident (auto or manual) |
 | i_assign | Assign incident (auto or manual) |
+| i_a_rspd | Add responders |
 | i_snooze | Manually snooze incident |
 | i_wake | Cancel snooze |
 | i_ack | Manually acknowledge incident |
@@ -203,7 +202,6 @@ Enter the integration name and description for easy management.
 
 | Config Item | Description |
 | :--- | :--- |
-| **Managing Team** | Select the team that manages this integration; only team members can edit the integration configuration |
 | **Endpoint** | HTTP/HTTPS address to receive callbacks, must start with `http://` or `https://` |
 | **TLS Verification** | Enabled by default. When disabled, TLS certificate verification of the target server is skipped; suitable for test environments or self-signed certificates |
 | **Headers** | Custom request headers in Key-Value format; multiple headers supported |
@@ -214,6 +212,44 @@ Enter the integration name and description for easy management.
 Disabling TLS certificate verification may expose you to man-in-the-middle attacks. Only disable it in test environments or when using self-signed certificates.
 </Warning>
 
+### Custom request body
+
+By default, the system pushes the complete JSON data following the [Payload structure](#request-payload) described above. If your receiver requires a specific data format, you can use a **custom request body** to reorganize the push content.
+
+Use `{{field.path}}` syntax to reference any field from the default Payload. The system replaces variables with actual values at push time.
+
+**Variable syntax:**
+
+- Use `.` to separate path levels, e.g. `{{incident.title}}` references the incident title
+- Array index access is supported, e.g. `{{incident.responders.0.email}}` references the first responder's email
+- When the entire value is a single variable (e.g. `"{{incident.labels}}"`), the original data type is preserved (object, array, number, etc.)
+- When a variable is mixed with other text (e.g. `"Incident: {{incident.title}}"`), the variable is converted to a string for concatenation
+
+**Example:**
+
+Transform the default Payload into a custom format for an internal system:
+
+```json
+{
+  "msg_type": "incident",
+  "event": "{{event_type}}",
+  "content": {
+    "id": "{{incident.incident_id}}",
+    "name": "{{incident.title}}",
+    "severity": "{{incident.incident_severity}}",
+    "status": "{{incident.progress}}",
+    "channel": "{{incident.channel_name}}",
+    "url": "{{incident.detail_url}}",
+    "labels": "{{incident.labels}}",
+    "responders": "{{incident.responders}}"
+  }
+}
+```
+
+<Tip>
+If a variable path does not exist in the default Payload, the system keeps the original `{{...}}` text without replacement. It is recommended to first check the actual default Payload via invocation history to confirm available field paths.
+</Tip>
+
 ## 4. Invocation History
 
 Incident Webhook provides a complete invocation history, helping you troubleshoot push delivery and debug callback interfaces.