chore(docs): Updated API Reference (v2) (#9437)

Automated changes by [create-pull-request](https://github.com/peter-evans/create-pull-request) GitHub action

Co-authored-by: Shahed Nasser <27354907+shahednasser@users.noreply.github.com>

www/apps/api-reference/specs/admin/paths/admin_fulfillments.yaml

@@ -30,6 +30,8 @@ post:
           if a field is prefixed with `+` it will be added to the default
           fields, using `-` will remove it from the default fields. without
           prefix it will replace the entire default fields.
+        externalDocs:
+          url: '#select-fields-and-relations'
   security:
     - api_token: []
     - cookie_auth: []