Document CX Score attributes in custom_attributes schema

The "CX Score rating" and "CX Score explanation" conversation attributes
are already returned in the API but were not mentioned in the OpenAPI spec.
This adds them to the custom_attributes description and examples across
versions 2.13, 2.14, 2.15, and Preview.

Closes intercom/intercom#433818

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: ellicenelson

descriptions/0/api.intercom.io.yaml

@@ -22789,7 +22789,8 @@ components:
       type: object
       description: An object containing the different custom attributes associated
         to the conversation as key-value pairs. For relationship attributes the value
-        will be a list of custom object instance models.
+        will be a list of custom object instance models. System-defined attributes
+        such as "CX Score rating" and "CX Score explanation" may also be included.
       additionalProperties:
         anyOf:
         - type: string
@@ -22802,6 +22803,9 @@ components:
         team_mates: 9
         start_date_iso8601: "2023-03-04T09:46:14Z"
         end_date_timestamp: 1677923174
+        CX Score rating: 4
+        CX Score explanation: The conversation was resolved quickly and the customer
+          expressed satisfaction with the outcome.
     custom_object_instance:
       title: Custom Object Instance
       type: object

descriptions/2.13/api.intercom.io.yaml

@@ -16920,7 +16920,8 @@ components:
       type: object
       description: An object containing the different custom attributes associated
         to the conversation as key-value pairs. For relationship attributes the value
-        will be a list of custom object instance models.
+        will be a list of custom object instance models. System-defined attributes
+        such as "CX Score rating" and "CX Score explanation" may also be included.
       additionalProperties:
         anyOf:
         - type: string

descriptions/2.14/api.intercom.io.yaml

@@ -18580,7 +18580,8 @@ components:
       type: object
       description: An object containing the different custom attributes associated
         to the conversation as key-value pairs. For relationship attributes the value
-        will be a list of custom object instance models.
+        will be a list of custom object instance models. System-defined attributes
+        such as "CX Score rating" and "CX Score explanation" may also be included.
       additionalProperties:
         anyOf:
         - type: string
@@ -18593,6 +18594,9 @@ components:
         team_mates: 9
         start_date_iso8601: "2023-03-04T09:46:14Z"
         end_date_timestamp: 1677923174
+        CX Score rating: 4
+        CX Score explanation: The conversation was resolved quickly and the customer
+          expressed satisfaction with the outcome.
     custom_object_instance:
       title: Custom Object Instance
       type: object

descriptions/2.15/api.intercom.io.yaml

@@ -19307,7 +19307,8 @@ components:
       type: object
       description: An object containing the different custom attributes associated
         to the conversation as key-value pairs. For relationship attributes the value
-        will be a list of custom object instance models.
+        will be a list of custom object instance models. System-defined attributes
+        such as "CX Score rating" and "CX Score explanation" may also be included.
       additionalProperties:
         anyOf:
         - type: string
@@ -19320,6 +19321,9 @@ components:
         team_mates: 9
         start_date_iso8601: "2023-03-04T09:46:14Z"
         end_date_timestamp: 1677923174
+        CX Score rating: 4
+        CX Score explanation: The conversation was resolved quickly and the customer
+          expressed satisfaction with the outcome.
     custom_object_instance:
       title: Custom Object Instance
       type: object