message: Add a warning to the deprecated non-eventsource sync endpoint
diff: @@ -127,6 +127,9 @@ export async function createRouter({
  await docsSynchronizer.doSync(
  () => {
  if (req.header('accept') !== 'text/event-stream') {
  + console.warn(
  + "The /sync/:namespace/:kind/:name endpoint but the call wasn't done by an EventSource. This behavior is deprecated and will be removed soon. Make sure to update the @backstage/plugin-techdocs package in the frontend to the latest version.",
  + );
  return createHttpResponse(res);
  }
  