fix: Support auth by sending cookies in scaffolder eventstream request

Signed-off-by: Erik Larsson <erik.larsson@schibsted.com>

.changeset/mighty-bats-nail.md

@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-scaffolder': patch
+---
+
+Support auth by sending cookies in eventstream request

plugins/scaffolder/src/api.ts

@@ -196,7 +196,7 @@ export class ScaffolderClient implements ScaffolderApi {
           const url = `${baseUrl}/v2/tasks/${encodeURIComponent(
             taskId,
           )}/eventstream`;
-          const eventSource = new EventSource(url);
+          const eventSource = new EventSource(url, { withCredentials: true });
           eventSource.addEventListener('log', (event: any) => {
             if (event.data) {
               try {