fix: openapi schema to handle additional attachments field in postsobject

public/openapi/components/schemas/PostsObject.yaml

@@ -2,4 +2,15 @@ PostsObject:
   description: One of the objects in the array returned from `Posts.getPostSummaryByPids`
   type: array
   items:
-    $ref: ./PostObject.yaml#/PostObject
+    allOf:
+      - $ref: ./PostObject.yaml#/PostObject
+      - type: object
+        description: Optional properties that may or may not be present (except for `pid`, which is always present, and is only here as a hack to pass validation)
+        properties:
+          pid:
+            type: number
+            description: A post identifier
+          attachments:
+            type: array
+        required:
+          - pid