add custom comment schema

docs/api/apiv3/components/schemas/custom_comment_properties.yml

@@ -0,0 +1,12 @@
+# Schema: CustomCommentProperties
+---
+type: object
+patternProperties:
+  "^customComment\\d+$":
+    type:
+      - "null"
+      - string
+    description: |-
+      A plain-text comment associated with a project custom field that has comments enabled.
+
+      The property is only present when the corresponding `customField{N}` has `has_comment` set to `true`.

docs/api/apiv3/openapi-spec.yml

@@ -749,6 +749,8 @@ components:
       "$ref": "./components/schemas/project_configuration_model.yml"
     CustomActionModel:
       "$ref": "./components/schemas/custom_action_model.yml"
+    CustomCommentProperties:
+      "$ref": "./components/schemas/custom_comment_properties.yml"
     CustomFieldLinkedProperties:
       "$ref": "./components/schemas/custom_field_linked_properties.yml"
     CustomFieldProperties: