Document CX Score attributes in custom_attributes schema (#446)

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

@@ -22889,7 +22889,8 @@ 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
@@ -22902,6 +22903,9 @@ 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

@@ -16933,7 +16933,8 @@ 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

@@ -18593,7 +18593,8 @@ 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
@@ -18606,6 +18607,9 @@ 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

@@ -19320,7 +19320,8 @@ 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
@@ -19333,6 +19334,9 @@ 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