POST call to /v1.0/sites/{siteId}/site-pages returns UnsupportedOperationException

Issue

• When trying to add a page via headless API using the POST endpoint /v1.0/sites/{siteId}/site-pages, UnsupportedOperationException is returned.

Environment

• Liferay DXP 7.4 Quarterly Release

Resolution

•  This API needs portal-ext.properties to have feature.flag.LPS-178052=true setting.
  A simple example of a curl command to invoke it would be:
  

  curl -X 'POST' 'http://localhost:8080/o/headless-delivery/v1.0/sites/33791/site-pages' -d $'{"title": "help"}' --header 'Content-Type: application/json' -u '[e-mail]:test'

Additional Information

• Please note, that Do note that, the Epic implementing this feature has the following comment:
  

  After MVP 1 and 2, we decide to change the approach of the feature so we close this epic and we'll open a new one.

  This means, that this is a discarded feature that is currently only available in the product for testing purposes.