* Return not found when request for content references when entity does not exist. * Apply suggestions from code review Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com> * Move check for entity existence from controller to the service. * Update OpenApi.json. * Apply suggestions from code review Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com> * Addressed points raised in code review. * Update OpenApi.json * Resolved breaking changes. --------- Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>