Overlay license in OpenAPI output (#2817)

Author: lcawl

docs/overlays/elasticsearch-serverless-openapi-overlays.yaml

@@ -11,6 +11,9 @@ actions:
         **Technical preview**  
         This functionality is in technical preview and may be changed or removed in a future release.
         Elastic will work to fix any issues, but features in technical preview are not subject to the support SLA of official GA features.
+      license:
+        name: Attribution-NonCommercial-NoDerivatives 4.0 International
+        url: 'https://creativecommons.org/licenses/by-nc-nd/4.0/'
       x-feedbackLink:
         label: Feedback
         url: https://github.com/elastic/docs-content/issues/new?assignees=&labels=feedback%2Ccommunity&projects=&template=api-feedback.yaml&title=%5BFeedback%5D%3A+